Alta definición
Registro en forodvd
+ Responder tema
Página 1 de 5 123 ... ÚltimoÚltimo
Resultados 1 al 15 de 73

Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

  1. #1
    Moderador Avatar de JDPBILI
    Registro
    29 oct, 04
    Ubicación
    VLC
    Mensajes
    9,914
    Agradecido
    7725 veces

    Predeterminado Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Regístrate para eliminar esta publicidad

    Abro este tema para debatir un poco sobre el tema.

    Algunos subwoofers pueden alcanzar frecuencias en las que en algunas ocasiones "no hay contenido" (tema software), nuestra capacidad auditiva no alcanza (oído), etc. pero los podemos implantar en un sistema.

    Influye -y mucho- varios factores: el más importante la existencia del canal LFE con un contenido "especifico" para estas frecuencias, con una conectividad especifica, etc. tampoco hay que dejar atrás el "complementar" altavoces que muchas veces no dan el "Do de pecho" en cuanto a graves.

    Está claro que cualquier subwoofer cuenta como mínimo con drivers de 8" y amplificadores de 100W (esto sería lo mínimo deseable, aunque los haya con especificaciones menores), y esto ya complementa muchos altavoces del mercado por abajo, y si hablamos de drivers de 10"/12" para arriba es más que evidente el plus que aportan. ¡¡¡ Que envidia me dais con esos bicharracos !!!.


    Pero además entiendo que entra en juego "la búsqueda del mejor sonido", la respuesta de frecuencia más amplia, completa, etc. pero la pregunta es.....¿ por qué no la buscamos también por arriba ?

    Es cierto que los altavoces hoy en día tienen cierta facilidad para llegar a frecuencias del orden de 25.000/30.000 hz con relativa facilidad, lo que cubre la "necesidad" de cualquier CD y la mayoría de los vinilos, pero también tenemos contenido por encima de estas frecuencias (formatos de alta resolución, SACD, etc. ).

    También es cierto que no hay un canal especifico o una conectividad "determinada", pero los supertweeters se pueden conectar bien directamente a las cajas o a filtros externos (esto es más tedioso) y en cambio no los tenemos en nuestros equipos.

    También hay muchísimas limitaciones, de hecho las mismas que numeraba para los subwoofers, pero no los montamos...

    Por otro lado son muy pocas las cajas del mercado que tienen integrados supertweeters...









    Es decir, no sería la "la leche" tener una respuesta de frecuencia entre 15-75.000 hz en nuestros equipos.....técnicamente ya es posible, pero solo parece que la buscamos por abajo...
    input y Titis han agradecido esto.
    Juan DP










  2. #2
    Learning to Live Avatar de raul_cegarra
    Registro
    23 feb, 13
    Mensajes
    562
    Agradecido
    963 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Para mi está claro, en audiometría no paso de 18khz y ya no es que no oiga, es que no "noto", no "siento" nada. En cambio, por debajo de 25hz, no sé si es oído o percepción, pero sí que dichas frecuencias se "sienten".

    Obviamente frecuencias muy muy bajas (del orden de 12hz hacia abajo), nos dice la física que no vamos a oirlas, pero se pueden sentir, eso sí, para sentir esas frecuencias taan bajas hemos de tener subs de la leche, porque no vale que esos 12hz sean a 50db, ya que ahí si que no vamos a notar nada.

    un saludo
    JDPBILI, lemg, Huguito y 1 usuarios han agradecido esto.
    "Always Never The Same"

  3. #3
    Pasaba por aquí... Avatar de lemg
    Registro
    10 dic, 04
    Ubicación
    Gran Canaria
    Mensajes
    1,961
    Agradecido
    4052 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Exacto, por arriba ni escuchamos ni sentimos nada, por debajo es cierto que no escuchamos, pero sentimos, es decir, la energía de esas ondas con un buen subwoofer es elevada y las vibraciones que genera son notables y eso es lo que busca en mi opinión el canal LFE, son efectos que se sienten en lugar que escucharse.

    Se busca un efecto similar (salvando las diferencias, claramente) a cualquier vibración de baja frecuencia que se generan en explosiones, derrumbes, temblores (¿nadie ha sentido en su casa cuando asfaltando la calle pasa la apisonadora?), etc. No las escuchamos, pero se sienten.

    Por arriba no ocurre lo mismo, dada su corta longitud de onda, direccionalidad y poca energía, ni escuchamos ni sentimos.

    Saludos.
    JDPBILI, atcing, Mike43 y 1 usuarios han agradecido esto.
    Antonio Díaz Rodríguez
    Agüimes - Gran Canaria

  4. #4
    licenciado Avatar de atcing
    Registro
    15 jul, 08
    Mensajes
    23,424
    Agradecido
    26192 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Cita Iniciado por JDPBILI Ver mensaje
    Abro este tema para debatir un poco sobre el tema.

    Algunos subwoofers pueden alcanzar frecuencias en las que en algunas ocasiones "no hay contenido" (tema software), nuestra capacidad auditiva no alcanza (oído), etc. pero los podemos implantar en un sistema.

    Influye -y mucho- varios factores: el más importante la existencia del canal LFE con un contenido "especifico" para estas frecuencias, con una conectividad especifica, etc. tampoco hay que dejar atrás el "complementar" altavoces que muchas veces no dan el "Do de pecho" en cuanto a graves.

    Está claro que cualquier subwoofer cuenta como mínimo con drivers de 8" y amplificadores de 100W (esto sería lo mínimo deseable, aunque los haya con especificaciones menores), y esto ya complementa muchos altavoces del mercado por abajo, y si hablamos de drivers de 10"/12" para arriba es más que evidente el plus que aportan. ¡¡¡ Que envidia me dais con esos bicharracos !!!.


    Pero además entiendo que entra en juego "la búsqueda del mejor sonido", la respuesta de frecuencia más amplia, completa, etc. pero la pregunta es.....¿ por qué no la buscamos también por arriba ?

    Es cierto que los altavoces hoy en día tienen cierta facilidad para llegar a frecuencias del orden de 25.000/30.000 hz con relativa facilidad, lo que cubre la "necesidad" de cualquier CD y la mayoría de los vinilos, pero también tenemos contenido por encima de estas frecuencias (formatos de alta resolución, SACD, etc. ).

    También es cierto que no hay un canal especifico o una conectividad "determinada", pero los supertweeters se pueden conectar bien directamente a las cajas o a filtros externos (esto es más tedioso) y en cambio no los tenemos en nuestros equipos.

    También hay muchísimas limitaciones, de hecho las mismas que numeraba para los subwoofers, pero no los montamos...

    Por otro lado son muy pocas las cajas del mercado que tienen integrados supertweeters...









    Es decir, no sería la "la leche" tener una respuesta de frecuencia entre 15-75.000 hz en nuestros equipos.....técnicamente ya es posible, pero solo parece que la buscamos por abajo...
    La diferencia está en que por abajo a cierto SPL se nota, pero por arriba no.
    En el caso de los subs con poco más de 90dB ya notas los 15hz (niveles que en sala puede lograr cualquier sub). Por ejemplo, un GTO de 12", algún modelo de Mac audio de 12", Infinity de 12", o RE Audio de 12" (entre seguro otros) en diseño sellado casi los dan ya en anecoica; ubicado en sala a esas frecuencias tan bajas con total seguridad los pasas. No es muy difícil pasar de 90dB en 15hz en sala; otro tema sería dar 100dB en 10hz... aunque de nuevo la ganancia de sala (mayor cuanto más abajo) puede ayudar.


    Un saludete
    JDPBILI y Mike43 han agradecido esto.
    "Nunca se conoce realmente a un hombre hasta que uno se ha calzado sus zapatos y caminado con ellos". - Matar a un Ruiseñor

    "Las burlas e insultos son las armas de quienes carecen de argumentación"

  5. #5
    Anonimo26102016
    Invitado

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    V.O. AlfonsoX
    JDPBILI ha agradecido esto.

  6. #6
    licenciado Avatar de atcing
    Registro
    15 jul, 08
    Mensajes
    23,424
    Agradecido
    26192 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Cita Iniciado por AlfonsoX Ver mensaje
    Hombreee algo interesante se lee por estos lares de vez en cuando.
    Claro que si JBILI los que no somos del Nepal creo que tenemos 5 sentidos, el oido es uno, pero la percepción del sonido no solo esta en el oido.
    En las frecuencias graves si bajamos del umbral de audición, lo sentimos en los pies en el estomago en los pelos de los brazos(el que tenga) y en otros dependiendo de la vestimenta, acuerdate de las KEF 107 Kube, que tenian el ampli que generaba por debajo de 20 Hz,
    en una Disco a tope se nota pero en casa tambien entiendo que es saludable que a menos volumen notemos cosas.
    En la zona ALta igual las ya viejas Sensys 2 tenian super agudos, y con la teoria en la mano no se escucha, pero sonaban mejor las del altavoz con el super agudos.
    Por otro lado si miras el rango de frecuencias de las modelos tope de cualquier marca, suben muchisimo, quiero decir que tienen capacidad para hacerlo y no se si se escuchan o no pero tambien suenan mejor, que un altavoz de agudos de batalla.
    Un par de ejemplos
    B&W 805 D3 de 34Hz-35KHz
    Diabo Utopia de 44Hz-40KHz
    G Utopia de 18Hz -40KH

    Demasiado tajante te veo en ese comentario, vibraciones de alta frecuencia entre 80K-120K no se sienten, pero diselo a gente que hatenido daños graves en organos internos, los crew de los carriers que curraban al lado de reactores puros al final se tenian que poner faja cuando se descubrio el porque, yo estas cosas como Dios que ni creo ni lo niego.
    Un saludo
    Hay pruebas rigurosas que demuestran que las frecuencias más altas no dan plus alguno que no sea puro mito (de hecho sólo hay que realizar un blind test entre ruido rosa cortado a 20Khz vs extendido hasta 25Khz)... como por abajo también hay pruebas y estudios rigurosos que demuestran sí hay diferencias:


    http://docs.wind-watch.org/Swinbanks...bine-Noise.pdf
    Thresholds of audibility for very lowâ€frequency pure tones

    Algunos que incluso se detecta desde niveles de SPL algo más bajos:







    https://en.wikipedia.org/wiki/Psycho...an_Hearing.svg


    Un saludete
    Última edición por atcing; 24/04/2016 a las 16:18
    JDPBILI ha agradecido esto.
    "Nunca se conoce realmente a un hombre hasta que uno se ha calzado sus zapatos y caminado con ellos". - Matar a un Ruiseñor

    "Las burlas e insultos son las armas de quienes carecen de argumentación"

  7. #7
    especialista Avatar de DiasDePlaya
    Registro
    02 oct, 14
    Mensajes
    2,666
    Agradecido
    3809 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Soy ignorante del tema, pero me parece que eso super agudos solo sirven para alterar a los perros, como los pitos de llamada que nosotros no escuchamos pero que para los perros son estrepitosos.
    JDPBILI ha agradecido esto.

  8. #8
    Anonimo26102016
    Invitado

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Ahhhhhhhhhhhh, yo escuche una vez decir a un Físico; El Universo es infinito, pero limitado”, que venga Acting y lo vea. (por que en mi cabeza no entra)
    En todo tema que está al límite del conocimiento, y los ultrasonidos y nuestra percepción de los mismo podria ser uno, aparecen diversas teorías y si alguien las plasma en un papel, para mí no es Dogma ni estudio concluyente.
    En una comunidad ponen un repetidor de telefonía y a 3 vecinos les duele la cabeza a 22 no les pasa nada y a otro se le pone el pene más erecto y, los estudios dirán A o B.
    Saliéndome del hilo un poco lanzo 2 preguntas trampa:
    En unas clases de radio-comunicaciones que impartía un Doctor Americano, a modo de introducción para soltar tensiones, comenzó a hablar de temas banales y curiosidades que se producían……..con las ondas de radio y una de las que conto, es que de las llamas sale sonido.
    El experimento es el siguiente en la base de la estructura de una antena de alta potencia, nos ponemos con10 kilos de papel de periódico y hacemos una hoguera, pues en las llamas se escucha lo que está emitiendo la antena. En aquel día no sabía explicar este hombre el por qué (pero una tarde hicimos la prueba y es cierto).
    Siguiente pregunta, a mí me tocó la triste tarea de confeccionar Informe por la muerte de un Soldado en la Estación Radar de Calatayud del EA, que penetro dentro del recinto de seguridad cercado (TOTALMENTE PROHIBIDO) y tras 2 horas de exposición, le provocó una Leucemia que acabo con su vida.
    Y el sonido son ondas y la pregunta es A esas ondas audibles que viajan bonitas como las de un estanque que les pasaría si hubiese otras de más frecuencia en el camino ¿serian iguales?(las ondas bonitas) ¿Cambiarían? ¿Cambiaria nuestra percepción?.
    Esto es algo que hace tiempo se lee y escucha y no está muy claro, por lo cual como a LEMG le decía, yo ni lo afirmo ni lo niego lo de Dios y también está muy claro en la Biblia
    Posiblemente, el vecino de las erecciones vigorosas, las tenga por que ha comprado nuevas publicaciones XXX o por la antena. Los sensYs 2 con ultraagudos me sonaban mejor igual llevaba menos cera en los oidos, pero no creo que sea prudente por parte de nadie decir eso es un cuento esta comprobado, estudios rigurosos.....bueno bueno bueno, que cada dia aprendemos cosas nuevas
    Un saludo

  9. #9
    Moderador Avatar de JDPBILI
    Registro
    29 oct, 04
    Ubicación
    VLC
    Mensajes
    9,914
    Agradecido
    7725 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Os pongo un texto interesante que he encontrado al respecto:

    El estudio íntegro, aquí: http://jn.physiology.org/content/83/6/3548

    Inaudible High-Frequency Sounds Affect Brain Activity: Hypersonic Effect

    Tsutomu Oohashi, Emi Nishina, Manabu Honda, Yoshiharu Yonekura, Yoshitaka Fuwamoto, Norie Kawai, Tadao Maekawa, Satoshi Nakamura, Hidenao Fukuyama, Hiroshi Shibasaki
    Journal of Neurophysiology Published 1 June 2000 Vol. 83 no. 6, 3548-3558 DOI:


    Abstract

    Although it is generally accepted that humans cannot perceive sounds in the frequency range above 20 kHz, the question of whether the existence of such “inaudible” high-frequency components may affect the acoustic perception of audible sounds remains unanswered. In this study, we used noninvasive physiological measurements of brain responses to provide evidence that sounds containing high-frequency components (HFCs) above the audible range significantly affect the brain activity of listeners. We used the gamelan music of Bali, which is extremely rich in HFCs with a nonstationary structure, as a natural sound source, dividing it into two components: an audible low-frequency component (LFC) below 22 kHz and an HFC above 22 kHz. Brain electrical activity and regional cerebral blood flow (rCBF) were measured as markers of neuronal activity while subjects were exposed to sounds with various combinations of LFCs and HFCs. None of the subjects recognized the HFC as sound when it was presented alone. Nevertheless, the power spectra of the alpha frequency range of the spontaneous electroencephalogram (alpha-EEG) recorded from the occipital region increased with statistical significance when the subjects were exposed to sound containing both an HFC and an LFC, compared with an otherwise identical sound from which the HFC was removed (i.e., LFC alone). In contrast, compared with the baseline, no enhancement of alpha-EEG was evident when either an HFC or an LFC was presented separately. Positron emission tomography measurements revealed that, when an HFC and an LFC were presented together, the rCBF in the brain stem and the left thalamus increased significantly compared with a sound lacking the HFC above 22 kHz but that was otherwise identical. Simultaneous EEG measurements showed that the power of occipital alpha-EEGs correlated significantly with the rCBF in the left thalamus. Psychological evaluation indicated that the subjects felt the sound containing an HFC to be more pleasant than the same sound lacking an HFC. These results suggest the existence of a previously unrecognized response to complex sound containing particular types of high frequencies above the audible range. We term this phenomenon the “hypersonic effect.”


    Aparte de lo que atañe a este estudio y el objeto de este hilo, es muy interesante lo mencionado en el este párrafo introductorio acerca del estudio de Muraoka en 1978 acerca de la calidad percibida a partir de 15 kHz...

    [QUOTE]INTRODUCTION

    It is generally accepted that audio frequencies above 20 kHz do not affect human sensory perception since they are beyond the audible range (Durrant and Lovrinc 1977; Snow 1931; Wegel 1922). Thus for example, most of the conventional commercial digital audio formats [e.g., compact disks (CDs), digital audio tapes (DATs), and digital audio broadcasting] have been standardized to a frequency range that does not allow such high-frequency components (HFCs) of sounds to be included. As a premise for determining these formats, several psychological experiments were performed to evaluate sound quality subjectively by means of questionnaires, according to the recommendation of the ComitéConsultatif International Radiophonique (CCIR 1978) or its modified versions. Studies by Muraoka et al. (1978)and Plenge et al. (1979), as well as other studies, concluded that listeners did not consciously recognize the inclusion of sounds with a frequency range above 15 kHz as making a difference in sound quality. Nevertheless, and interestingly enough, artists and engineers working to produce acoustically perfect music for commercial purposes are convinced that the intentional manipulation of HFC above the audible range can positively affect the perception of sound quality (Neve 1992). Indeed, the Advanced Audio Conference organized by the Japan Audio Society (1999) proposed two next-generation advanced digital audio formats: super audio compact disk (SACD) and digital versatile disk audio (DVD-audio). These formats have a frequency response of up to 100 kHz and 96kHz, respectively. However, the proposal was not based on scientific data about the biological effects of the HFCs that would become available with these advanced formats. Although recently there have been several attempts to explore the psychological effect of inaudible HFCs on sound perception using a digital audio format with a higher sampling rate of 96 kHz (Theiss and Hawksford 1997; Yamamoto 1996; Yoshikawa et al. 1995,1997), none of these studies has convincingly explained the biological mechanism of the phenomenon. This may reflect in part the limitations of the conventional audio engineering approach for determining sound quality, which is solely based on a subjective evaluation obtained via questionnaires.


    There are two factors that may have some bearing on this issue. First, it has been suggested that infrasonic exposure may possibly have an adverse effect on human health (Danielsson and Landstrom 1985), suggesting that the biological sensitivity of human beings may not be parallel with the “conscious” audibility of air vibration. Second, the natural environment, such as tropical rain forests, usually contains sounds that are extremely rich in HFCs over 100 kHz. From an anthropogenetic point of view, the sensory system of human beings exposed to a natural environment would stand a good chance of developing some physiological sensitivity to HFCs. It is premature to conclude that consciously inaudible high-frequency sounds have no effect on the physiological state of listeners.



    In the present study, therefore, we addressed this issue by using quantifiable and reproducible measurements of brain activity. To measure human physiological responses to HFCs, we selected two noninvasive techniques: analysis of electroencephalogram (EEG) and positron emission tomography (PET) measurements of the regional cerebral blood flow (rCBF). These methods have complementary characteristics. EEG has excellent time resolution, is sensitive to the state of human brain functioning, and places fewer physical and mental constraints on subjects than do other techniques such as functional magnetic resonance imaging (fMRI). This is of special importance because some responses might be distorted by a stressful measurement environment itself. On the other hand, PET provides us with detailed spatial information on the neuroanatomical substrates of brain activity. Combining these two techniques with psychological assessments, we provide evidence herein that inaudible high-frequency sounds have a significant effect on humans.
    [/QUOTE


    METHODS

    Subjects

    Twenty-eight Japanese volunteers (15 males and 13 females, 19–43 years old) participated in the EEG experiments; 12 Japanese volunteers (8 males and 4 females, 19–34 years old) participated in the PET experiment; and 26 Japanese volunteers (15 males and 11 females, 18–31 years old) participated in the psychological experiment. None of the subjects had any history of neurological or psychiatric disorders. Written informed consent was obtained from all subjects before the experiments. The PET and EEG experiments were performed in accordance with the approval of the Committee of Medical Ethics, Graduate School of Medicine, Kyoto University. All subjects were familiar with the actual sounds of the instruments used as a sound source.

    Sound materials and presentation systems

    Traditional gamelan music of Bali Island, Indonesia, a natural sound source containing the richest amount of high frequencies with a conspicuously fluctuating structure, was chosen as the sound source for all experiments. A traditional gamelan composition, “Gambang Kuta,” played by “Gunung Jati,” an internationally recognized gamelan ensemble from Bali, was recorded using a B&K 4135 microphone, a B&K 2633 microphone preamplifier, and a B&K 2804 power supplier, all manufactured by Brüel and Kjær (Nærum, Denmark). The signals were digitally coded by Y. Yamasaki's high-speed one-bit coding signal processor (United States Patent No. 5351048) (Yamasaki 1991) with an A/D sampling frequency of 1.92 MHz and stored in a DRU-8 digital data recorder (Yamaha, Hamamatsu, Japan). This system has a generally flat frequency response of over 100 kHz.

    Most of the conventional audio systems that have been used to present sound for determining sound quality were found to be unsuitable for this particular study. In the conventional systems, sounds containing HFCs are presented as unfiltered source signals through an all-pass circuit and sounds without HFCs are produced by passing the source signals through a low-pass filter (Muraoka et al. 1978;Plenge et al. 1979). Thus the audible low-frequency components (LFCs) are presented through different pathways that may have different transmission characteristics, including frequency response and group delay. In addition, inter-modulation distortion may differentially affect LFCs. Therefore it is difficult to exclude the possibility that any observed differences between the two different sounds, those with and those without HFCs, may result from differences in the audible LFCs rather than from the existence of HFCs. To overcome this problem, we developed a bi-channel sound presentation system that enabled us to present the audible LFCs and the nonaudible HFCs either separately or simultaneously. First, the source signals from the D/A converter of Y. Yamasaki's high-speed, one-bit coding signal processor were divided in two. Then, LFCs and HFCs were produced by passing these signals through programmable low-pass and high-pass filters (FV-661, NF Electronic Instruments, Tokyo, Japan), respectively, with a crossover frequency of 26 or 22 kHz and a cutoff attenuation of 170 or 80 dB/octave, depending on the type of test. Then, LFCs and HFCs were separately amplified with P-800 and P-300L power amplifiers (Accuphase, Yokohama, Japan), respectively, and presented through a speaker system consisting of twin cone-type woofers and a horn-type tweeter for the LFCs and a dome-type super tweeter with a diamond diaphragm for the HFCs. The speaker system was designed by one of the authors (T. Oohashi) and manufactured by Pioneer Co., Ltd. (Tokyo, Japan). This sound reproduction system had a flat frequency response of over 100 kHz. The level of the presented sound pressure was individually adjusted so that each subject felt comfortable; thus the maximum level was approximately 80–90 dB sound pressure level (SPL) at the listening position.

    Using the bi-channel sound presentation system, four different sound combinations were prepared as follows: 1) full-range sound (FRS) = HFC + LFC; 2) high-cut sound (HCS) = LFC only; 3) low-cut sound (LCS) = HFC only; and,4) baseline = no sound except for ambient noise. All experiments were performed in an acoustically shielded room. In the PET experiment, there was a very low-level fan noise from the PET scanner, which did not annoy the subjects. Figure1 A shows the averaged power spectrum of the source signal obtained from the music with a CF-5220 fast Fourier transform (FFT) analyzer (Ono Sokki, Tokyo, Japan) over an analysis period of 200 s. It contained a significant amount of HFCs above the audible range, often exceeding 50 kHz and, at certain times, 100 kHz. Figure 1 B shows the averaged power spectra of the actual sounds reproduced with a 22 kHz cutoff frequency for the filter and recorded at the subject's head position. The spectrum of FRS was essentially the same as that of the source and contained both LFCs below and HFCs above 22 kHz. None of the blindfolded subjects could distinguish LCS (i.e., HFC only) from silence when it was presented alone. Therefore we concluded that the HFC employed in the present experimental setting was, at least, a consciously unrecognizable air vibration.

    Fig. 1. Power spectra of the sound used in this study. A: the averaged power spectrum calculated from the entire 200-s period of the recorded sound source signal using a CF-5220 fast Fourier transform (FFT) analyzer (Ono Sokki, Tokyo, Japan). It contains a significant amount of high-frequency components above the audible range. B: the averaged power spectra of the sounds reproduced by the bi-channel sound presentation system (see text) in different conditions. The power was calculated from the signal actually recorded at the subject's head position using a B&K 4135 microphone (Brüel and Kjær, Nærum, Denmark). The top, middle, and bottom panels represent full-range sound (FRS), high-cut sound (HCS), and low-cut sound (LCS), respectively. The power spectrum of FRS is essentially identical to the spectrum of the source and contains both a low-frequency component (LFC) (i.e., the one used in the HCS condition) and a high-frequency component (HFC) (in the LCS condition).


    EEG recordings and analysis

    The EEG experiments were performed in the EEG laboratory of the National Institute of Multimedia Education. Subjects were asked to sit on a chair in a relaxed position. The distance from the speakers to the subjects' ears was approximately 2.5 m. Special attention was paid to the subjects' immediate environment to avoid discomfort. For example, the room was decorated with plants, lacquered masks, and landscape paintings. The equipment for the EEG recordings was hidden from the subjects' view and all cables for the experimental equipment were in a pit below the floor. The subjects were instructed to enjoy the music without any cognitive tasks during the sound presentation. The subjects were able to see outdoors through a wide, double-glass window that acoustically shielded the experimental room from outside sounds. Two different EEG experiments were performed. In the first experiment, to explore the physiological effect of sounds with a nonaudible frequency range, we employed a strictly controlled experimental setting of sound presentation combined with conventional EEG measurements. In the second experiment, the same effect was examined under more ordinary listening conditions.
    EXPERIMENT 1.

    To examine the physiological effect of sounds with an inaudible frequency range, 11 subjects were presented with the FRS, HCS, and baseline conditions. In this experiment, a cutoff frequency of 26 kHz with a steeper cutoff attenuation of 170 dB/octave was employed to separate HFCs from LFCs. This relatively high cutoff frequency was chosen because when a cutoff frequency lower than 26 kHz is used the skirts of the power spectrum of the filtered HFCs extend below 20 kHz and generate sounds containing components below 20 kHz. It is widely known that the upper limit of the audible range of humans varies considerably. It usually corresponds to around 15 or 16 kHz in young adults and sometimes below 13 kHz in the elderly, and some people can recognize air vibrations of 20 kHz as sound. When a cutoff frequency of 26 kHz is employed with the steeper cutoff attenuation, the power spectrum of the filtered HFCs under 20 kHz falls below the system noise level. Therefore we selected a cutoff frequency of 26 kHz, which is sufficiently high to completely exclude contamination by audible sound components in all of the subjects. In accordance with conventional recordings of background EEG activity, subjects were asked to keep their eyes naturally closed during the experiment to eliminate any effects of visual input. The presentation of the sounds in both FRS and HCS conditions lasted 200 s, which included the entire piece of music. The baseline condition also lasted 200 s without sound presentation. The inter-session intervals were 10 s. Two recording sessions were repeated for each condition in the following order: baseline–FRS–HCS–FRS–HCS–baseline.

    EXPERIMENT 2.

    The validity of the digital audio format internationally employed for CDs was evaluated under more ordinary listening conditions. Seventeen subjects were presented with sounds using a cutoff frequency of 22 kHz, which corresponds to the upper range of sounds recorded by a CD. Subjects were then asked to keep their eyes naturally open as they usually do when they listen to music. The open-eye condition was also appropriate to control the subjects' vigilance. Each subject was presented with four types of conditions: FRS, HCS, and baseline, as in Experiment 1, plus LCS to elucidate the effect of an HFC when it is presented alone. As in Experiment 1, each condition lasted 200 s. Before the actual recording sessions, HCS was presented once to familiarize the subjects with the experimental environment. To avoid any influence by the order of presentation, the four different conditions were performed in random order across the subjects. After a 10-min rest, the same four conditions were repeated in reverse order. Neither the subjects nor the experimenters knew which conditions were being performed.


    The EEGs, recorded using the WEE-6112 telemetric system (Nihon-Koden, Tokyo, Japan) to minimize constraint on the subjects, were stored on magnetic tape for off-line analysis. The EEGs were recorded continuously, including the intervals between the sessions. Data were recorded from 12 scalp sites (Fp1, Fp2, F7, Fz, F8, C3, C4, T5, Pz, T6, O1, and O2 according to the International 10-20 System) using linked earlobe electrodes as the reference with a filter setting of 1–60 Hz (−3 dB). The impedance of all electrodes was kept below 5 kΩ. The EEGs obtained were subjected to power spectra analysis. The power spectrum of the EEG at each electrode was calculated by fast Fourier transform (FFT) analysis for every 2-s epoch, with an overlap of 1 s, at a frequency resolution of 0.5 Hz with a sampling frequency of 256 Hz. Then the averaged power spectrum within a 10-s time window was calculated. Each analysis window was designated by the time at its middle point measured from the beginning of the sound presentation. For example, the time window labeled as 100-s contains data from 95 to 105 s from the beginning. Then the square root of the averaged power level in a frequency range of 8.0–13.0 Hz at each electrode position was calculated as the equivalent potential of EEGs in an alpha band (alpha-EEG). To eliminate a possible effect of inter-subject variability, the alpha-EEG at each electrode position was normalized with respect to the mean value across all time epochs, conditions, and electrode positions for each subject. To obtain an overview of the data, to check for contamination by artifacts, and to characterize the spatial distribution of the alpha-EEG, we constructed colored contour line maps using 2,565 scalp grid points with linear interpolation and extrapolation. This type of map is called a brain electrical activity map (BEAM) (Duffy et al. 1979). To avoid contamination by artifacts arising from eye movement, we calculated occipital alpha-EEGs by averaging the alpha-EEGs at the electrodes on the posterior one-third of the scalp. The BEAMs and occipital alpha-EEGs were averaged over multiple time epochs and subjected to a statistical evaluation of condition effects. Since the time course of the alpha-EEG change revealed a considerable time lag with respect to the sound presentation (see results and Fig.2C), we made a statistical evaluation of the data obtained from all time epochs as well as of the data from only the latter half of the session (from the 100-s to 200-s class marks). We used analysis of variance (ANOVA) followed by Fishers' protected least significant difference (PLSD) post hoc test to assess statistical significance for the different conditions.




    Fig. 2.
    Normalized potentials from the alpha frequency range of the spontaneous electroencephalogram (alpha-EEG) under each experimental condition (FRS, HCS, and baseline) and time course in the successive FRS and HCS conditions in EEG Experiment 1. A: brain electrical activity maps (BEAMs) averaged across the 11 subjects over the entire time epoch of sound presentation. Darker red indicates higher alpha-EEG potential. Note that the alpha-EEG is enhanced in the parieto-occipital region exclusively in the FRS condition. B: mean and standard error of the occipital alpha-EEG for all 11 subjects. FRS significantly enhanced the occipital alpha-EEG relative to HCS.C: time course of grand average BEAMs across all 11 subjects. Two sessions for each condition were averaged in this figure. The occipital alpha-EEG shows a gradual increase during the FRS presentation and a gradual decrease while HCS was successively presented



    Sigue......
    Última edición por JDPBILI; 24/04/2016 a las 20:02
    Anonimo26102016 ha agradecido esto.
    Juan DP










  10. #10
    Moderador Avatar de JDPBILI
    Registro
    29 oct, 04
    Ubicación
    VLC
    Mensajes
    9,914
    Agradecido
    7725 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    PET measurement and analysis

    The sound presentation equipment was installed and calibrated in the PET laboratory of Kyoto University Hospital. Subjects lay supine, with their eyes naturally open, on the PET scanner bed in a quiet, dimly lit room. Their heads were fixed in individually molded helmet-shaped rests that were contoured to leave their ears undisturbed. The distance from the speakers to the subjects' ears was approximately 1.5 m. As in the EEG study, special attention was paid to the immediate environment to minimize the subjects' discomfort. Six of the subjects were studied using FRS, HCS, and baseline conditions, and the other six were studied using FRS, LCS, and baseline conditions. The order of the conditions was randomized across the subjects and a total of six scans was performed on each subject with intervals of 7 min. For each of the FRS, HCS, and LCS presentations, 30 mCi of 15O-labeled water was injected into the right cubital vein 80 s after the beginning of each session. The same procedure was carried out for the baseline condition after a minimum 1-min rest without any presentation other than the ambient background noise of the PET scanner room. Following the injection, the head was scanned for radioactivity with a multi-slice PET scanner (PCT3600W, Hitachi Medical Co., Tokyo, Japan) for 120 s. The scanner acquired 15 slices with a center-to-center distance of 7 mm and an axial resolution of 6.5 mm full-width at half-maximum (FWHM) at the center (Endo et al. 1991). The in-plane spatial resolution with stationary mode acquisition used in this protocol was 6.7 mm of FWHM, which was blurred to ∼10 mm in the reconstructed PET images. The field of view and pixel size were 256 mm and 2 × 2 mm, respectively. Prior to the emission measurements, transmission data were obtained using a68Ge/68Ga standard plate source for attenuation correction. Reconstructed images were obtained by summing up the activity throughout the 120-s period. No arterial blood sampling was performed; therefore the images collected were of tissue activity. Tissue activity recorded by this method is linearly related to rCBF (Fox et al. 1984; Fox and Mintun 1989).
    The PET data were analyzed with statistical parametric mapping (SPM96 software, Wellcome Department of Cognitive Neurology, London, UK) implemented in MATLAB (Mathworks, Inc., Sherborn, MA). Statistical parametric maps are spatially extended statistical processes that are used to characterize regionally specific effects in imaging data (Friston et al. 1991, 1994,1995b; Worsley et al. 1992). The scans from each subject were realigned using the first image as the reference (Friston et al. 1995a). After realignment, the images were transformed into a standard anatomical space (Friston et al. 1995a; Talairach and Tournoux 1988). As a result, each scan was resampled into voxels that were 2 × 2 × 4 mm each in the x (right-left), y(anterior-posterior), and z (superior-inferior) directions. Each image was smoothed with an isotropic Gaussian kernel (FWHM = 15 mm) to account for the variation in normal gyral anatomy and to increase signal-to-noise ratio. The effect of global differences in rCBF between scans was removed by scaling the activity in each pixel proportional to the global activity so as to adjust the mean global activity of each scan to 50 ml/100g/min. To explore regions showing significant differences in rCBF among different conditions, the general linear model with contrasts was employed at each voxel (Friston et al. 1995b). Since the different conditions were run in different subjects, the contrasts of FRS versus HCS and HCS versus baseline were examined for six subjects, and those of FRS versus LCS and LCS versus baseline were examined for the other six subjects. The contrast of FRS versus baseline was examined for all 12 subjects, inclusive. The resulting set of voxel values for each contrast constituted a statistical parametric map of the t statistic. The t values were transformed into the unit normal distribution (Z score), which was independent of the degree of freedom of error, and were thresholded at 3.09. To account for multiple non-independent comparisons, the significance of the activation in each brain region detected was estimated by the use of distributional approximations from the theory of Gaussian fields in terms of spatial extent and/or peak height (Friston et al. 1994). An estimated P value of 0.05 was used as a final threshold for significance. The resulting set of Zscores for the significant brain regions was mapped onto a standard spatial grid (Talairach and Tournoux 1988).
    In all of the subjects, EEGs were simultaneously recorded throughout the PET measurement, which lasted approximately 60 min, from 12 electrodes as in the EEG experiment. The EEGs obtained during the total 200-s sound presentation were subjected to power spectra analysis and, in particular, those during each 120-s PET scan were used for correlation analysis with the rCBF. The data of one subject were excluded because of an excessive amount of electrical noise in the EEG. We used ANOVA followed by Fisher's PLSD post hoc test to assess the statistical significance of the different conditions. In addition, we used SPM software to calculate a correlation map between rCBF and the occipital alpha-EEG, to examine the relationship between them. An estimated P value of 0.05 with correction for multiple comparisons was used as the final threshold for significance.
    Psychological evaluation of sound quality

    We also evaluated the subjective perception of sound quality. Since the subjective impression of sounds is closely related to the subjects' psychological condition, this evaluation was performed separately from the EEG and PET experiments. We used the same piece of gamelan music as was used for the EEG and PET experiments. First, a pair of FRS and HCS, each lasting 200 s, was presented. The order of the conditions was randomized across the subjects. After an intermission of 3 min, another pair of FRS and HCS was presented in reverse order. Therefore the stimuli were presented in an A-B-B-A fashion, in which FRS and HCS were assigned to A and B or B and A, respectively, in a randomly counterbalanced way across the subjects. Neither the subjects nor the experimenter knew what the sound conditions were, although they did know that the presentation was in an A-B-B-A fashion. The subjects filled out a questionnaire to rate the sound quality in terms of 10 elements, each expressed in a pair of contrasting Japanese words (e.g., soft vs. hard). Each element of each condition was graded on a scale of 5 to 1. The scores were statistically evaluated by the paired comparison method described byScheffé (1952). Note that the method used in the present study differs from that recommended by the CCIR (1978) and its modified version, which were widely used to determine the digital format of CDs around 1980 (e.g.,Muraoka et al. 1978; Plenge et al. 1979). In the previous studies, sound materials were never longer than 20 s and the interval between two successive sound materials was 2–3 s or less. Therefore if neuronal response to sound stimuli is characterized by delay and persistence for longer than 20 s, it is difficult to exclude the possibility that those studies might have introduced a subjective evaluation that might not precisely correspond to each sound condition.



    RESULTS

    EEG Experiment 1

    Figure 2, A and B, shows the grand average BEAMs and occipital alpha-EEGs, respectively, for the 11 subjects, calculated over the entire period of the sound presentation. The alpha-EEGs were enhanced during FRS compared with those during the other conditions. This enhancement was especially predominant in the occipital and parietal regions (Fig. 2 A). ANOVA on the occipital alpha-EEG revealed a significant main effect of condition [F(2,63) = 3.74, P < 0.05]. The post hoc tests showed that the occipital alpha-EEG during FRS was significantly greater than that during HCS (P < 0.05) (Fig.2 B). There was a similar tendency when FRS was compared with the baseline (P = 0.10). Figure 2 C shows the averaged time course of the BEAMs calculated for each 30 s of the FRS and HCS conditions for all subjects, inclusive. The alpha-EEG showed a gradual increase during the first several tens of seconds of FRS; there was a gradual decrease at the beginning of the following HCS. Taking into account the delay and persistence of the enhancement of the alpha-EEG, statistical evaluation was also made of the data from the latter half of the recording session (from the 100-s to 200-s class mark). In this analysis, compared with the data obtained by analyzing the entire period of the sound presentation, ANOVA followed by post hoc tests revealed a more significant main effect of condition [F(2,63) = 4.43, P < 0.05] and a greater difference between FRS and HCS (P < 0.01).

    EEG Experiment 2

    The grand average BEAMs and occipital alpha-EEGs across all 17 subjects over the latter half of the session (from the 100-s to 200-s class mark) are shown in Fig. 3. The amount of eye movement did not differ for different conditions. The alpha-EEG showed significant enhancement in FRS compared with the other conditions (Fig. 3 A). This enhancement was predominant in the occipital and parietal regions. ANOVA on the occipital alpha-EEG revealed a significant main effect of condition [F(3,131) = 3.74,P < 0.05]. The post hoc tests showed that the occipital alpha-EEG in FRS was significantly greater than that in the other three conditions (Fig. 3 B). There was no significant difference among HCS, LCS, and baseline (P > 0.8 for all comparisons). A similar but weaker tendency was recognized when the data from the entire period of the sound presentation were subjected to the analysis (main effect of condition, P = 0.26; FRS vs. baseline, P = 0.05). This is reasonable because the time course of the grand average occipital alpha-EEG in this experiment showed, as in Experiment 1, a gradual increase over the first several tens of seconds of FRS (data not shown).



    Fig. 3.
    Normalized alpha-EEG potentials in each experimental condition (FRS, HCS, LCS, and baseline) during the latter half of the sound presentation in EEG Experiment 2. A: BEAMs averaged across all 17 subjects over the time period from the 100- to 200-s class marks. B: mean and standard error of the occipital alpha-EEG for all 17 subjects. FRS significantly enhanced the occipital alpha-EEG relative to the other conditions.



    PET experiment

    When the conditions with audible sounds (i.e., FRS or HCS) were compared with those without audible sounds (i.e., LCS or baseline), the bilateral temporal cortex, presumably the primary and secondary auditory cortex, always showed significantly increased rCBF as expected (Table 1; see also Fig. 5 C). More importantly, when FRS was compared with HCS, deep-lying structures in the brain were significantly more activated during the presentation of FRS than during that of HCS (Fig. 4and Table 1). The activated areas corresponded to the brain stem (Fig.4 B) and the lateral part of the left thalamus (Fig.4 C). The same areas also showed an increased rCBF when FRS was compared with either the baseline or LCS (Fig.5, A and B). This tendency was also recognizable in the comparison of FRS versus baseline with a lower threshold (Z > 1.64 with correction for multiple comparisons) (Fig. 5 C and Table 1). Conversely, when HCS was presented, these areas in fact showed a decreased rCBF compared with the baseline (Fig. 5, A and B). When LCS was compared with the baseline, no significant differential activation was observed anywhere in the brain and neither the left thalamus nor the brain stem showed changes in rCBF.

    ***** y como el artículo es mucho más extenso, para seguir leyéndolo y obtener las conclusiones, cito la fuente: http://jn.physiology.org/content/83/6/3548 *****
    Última edición por JDPBILI; 24/04/2016 a las 20:00
    input y Anonimo26102016 han agradecido esto.
    Juan DP










  11. #11
    Moderador Avatar de JDPBILI
    Registro
    29 oct, 04
    Ubicación
    VLC
    Mensajes
    9,914
    Agradecido
    7725 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    El estudio acaba con estas conclusiones:

    In conclusion, our findings that showed an increase in alpha-EEG potentials, activation of deep-seated brain structures, a correlation between alpha-EEG and rCBF in the thalamus, and a subjective preference toward FRS, give strong evidence supporting the existence of a previously unrecognized response to high-frequency sound beyond the audible range that might be distinct from more usual auditory phenomena. Additional support for this hypothesis could come from future noninvasive measurements of the biochemical markers in the brain such as monoamines or opioid peptides.
    atcing, input y Anonimo26102016 han agradecido esto.
    Juan DP










  12. #12
    gurú Avatar de input
    Registro
    15 nov, 10
    Mensajes
    10,380
    Agradecido
    9260 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Creo que todos o casi todos coincidimos en el tema de lso super tweeters, no por otra cosa que no sea naturaleza humana y sus incuestionables 20hz-20khz (en el mejor oido sano claro está).

    Sin embargo, con el sub es distinto como bien apuntáis, en als frecuencias ultra bajas y su posibilidad de notarlas por vibración o presión sonora.

    Esto es algo que he pensado desde siempre en relación con mi equipo: muchos sabéis que tengo uno de 8", el cual me da buen resultado, sobre todo si lo colocas en lugares estratégicos. Como no he probado otro, tengo la duda de si colocar uno de 12", a igual volumen, me daría esos efectos que habláis. No hablamos de volúmenes sonoros de despertar a la vecindad, sino a volúmenes medios bajos.

    S2...
    atcing ha agradecido esto.

  13. #13
    experto
    Registro
    05 nov, 10
    Ubicación
    Valencia
    Mensajes
    1,545
    Agradecido
    1056 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Hay que tener en cuenta que la mayoría de los amplificadores están "capados" por encima de los 20KHz.
    No os podeis imaginar las sorpresas que me he llevado cuando, una vez realizada una reparación, le hago un chequeo de respuesta en frecuencia a los equipos.
    atcing, Mike43, input y 1 usuarios han agradecido esto.
    Principal
    Emotiva UMC-200 + etapa atm mod. EPM1 20W pure class A + etapa atm EPM55 (5x180W) + Oppo BDP105 + iPlus + Vienna Acoustics Mozart Grand (trio frontal) + Linn Komponent 106 (surround) + Linn Afekt (sub) + Panasonic VT20 + Optoma HD25

    Despacho
    Emotiva Fusion 8100 + etapa atm miniEPM1 (8w pure class A)+ 5xLM3886 multichannel + Mac mini + PMC DB2 (frontales) + Electrovoice EV2 (surround) + Jamo tuneado (sub) + Dell 24"

  14. #14
    gurú Avatar de input
    Registro
    15 nov, 10
    Mensajes
    10,380
    Agradecido
    9260 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Cita Iniciado por jalejos Ver mensaje
    Hay que tener en cuenta que la mayoría de los amplificadores están "capados" por encima de los 20KHz.
    No os podeis imaginar las sorpresas que me he llevado cuando, una vez realizada una reparación, le hago un chequeo de respuesta en frecuencia a los equipos.
    Cuenta cuenta!!!!

  15. #15
    Solo se, que no se nada Avatar de ManuelBC
    Registro
    15 jun, 08
    Ubicación
    Barcelona
    Mensajes
    44,822
    Agradecido
    55754 veces

    Predeterminado Re: Ponemos SW por encima de nuestra capacidad auditiva, ¿por que no supertweeters ?

    Los agudos se van perdiendo con la edad, quizás los niños si puedan oír altas frecuencias que nosotros ya no escuchamos.

    Lástima que ya no recuerde como escuchaba con 7 o 10 años pero seguro que bastante mejor que ahora con casi ya 49
    Fotos Salón: OLED LG C1_65" + Nad T778 (ex Marantz SR6010) + Monitor Audio Gold 100 5G + Silver FX + SVS SB1000 + Philips CD630 + Zidoo Z9X + Auricules Meze Audio 99 Classics + Deco Satelite Iris 1802 4k
    Foto equipo estéreo Philips: Actualmente sin uso: FA650 + EQ670 + Phono + doble pletina + Sinton. + CD630 + B&W DM100i
    Dormitorio: Samsung UE40NU7192
    Cocina: LG 32LK6200PLA 32"

+ Responder tema
Página 1 de 5 123 ... ÚltimoÚltimo

Temas similares

  1. Memoria auditiva
    Por OrtoPiroMeta en el foro Tertulia
    Respuestas: 3
    Último mensaje: 28/02/2014, 22:52
  2. a que altura ponemos la tele
    Por tumbatorres en el foro TV: General y consejos de compra
    Respuestas: 3
    Último mensaje: 21/02/2010, 23:48
  3. Respuestas: 0
    Último mensaje: 08/10/2007, 20:30
  4. EL CLAN ¿QUE NOMBRE PONEMOS?
    Por MOLINA26 en el foro Videojuegos
    Respuestas: 13
    Último mensaje: 20/12/2006, 20:07
  5. mejora auditiva con lector de cd?
    Por BALDO en el foro Acústica (audiofília, tertulias audiófilas...)
    Respuestas: 9
    Último mensaje: 22/04/2005, 16:45

Permisos de publicación

  • No puedes crear nuevos temas
  • No puedes responder temas
  • No puedes subir archivos adjuntos
  • No puedes editar tus mensajes
  •  
Powered by vBulletin® Version 4.2.3
Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.
Search Engine Optimization by vBSEO
Image resizer by SevenSkins