Sound intensity

About: Sound intensity is a research topic. Over the lifetime, 4735 publications have been published within this topic receiving 54163 citations. The topic is also known as: sound energy flux density & sound power density.

Factors Influencing Acoustic Performance of Sound Absorptive Materials

Abstract: Today much importance is given to the acoustical environment. Noise control and its principles play an important role in creating an acoustically pleasing environment. This can be achieved when the intensity of sound is brought down to a level that is not harmful to human ears. Achieving a pleasing environment can be obtained by using various techniques that employ different materials. One such technique is by absorbing the sound. Fibrous, porous and other kinds of materials have been widely accepted as sound absorptive materials. This paper review and describes how the physical prosperities of materials like fiber type, fiber size, material thickness, density, airflow resistance and porosity can change the absorption behavior. The effect of surface impedance, placement / position of sound absorptive and compression, on sound absorption behavior of materials was also considered. The sound absorption of different fibrous materials was experimentally tested. The results shows the relationship between the sound absorption and airflow resistance, material thickness, air gap and attachment film. Higher airflow resistance always gives better sound absorption values but for airflow resistance higher than 1000 the sound absorption have less values because difficulty movements of sound wave through the materials. The creation of air gap, 5mm, 10 mm behind the absorptive material increases sound absorption coefficient values in mid and higher frequencies. There is not much difference seen between 5 mm air gap sample and 10 mm air gap sample. Moreover, maxima peak for different air gap is different (higher the air gap distance, maxima peak shift towards lower frequency

Coding of Amplitude and Frequency Modulated Sounds in the Cochlear Nucleus of the Rat

Abstract: The responses of single units in the cochlear nucleus of the rat to sinusoidally amplitude- and frequency-modulated tones and amplitude-modulated broadband noise were studied. The distribution of discharges within a cycle of modulation was determined from cycle histograms locked to the modulation wave. In response to amplitude-modulated tones and broadband noise, all units investigated showed a peak in the degree of modulation of the spike frequency within the modulation frequency range from 50 to 200 Hz. In many units the relationship between the degree of modulation of the stimulus sound and of the modulation of the resulting spike train was almost unchanged over a wide range of sound intensities. In other units, enhancement of modulation within a certain range of modulation frequency became more pronounced when the sound intensity was increased. This was mainly due to a suppression of modulation at lower modulation frequencies. The shape of the histograms was nearly sinusoidal even at modulation depths which resulted in nearly 100% modulation of the neural discharge frequency. The amount of modulation of the discharge frequency in response to frequency-modulated tones was dependent on the frequency of the tone in relation to the CF of the unit.

Active control of sound radiation using volume velocity cancellation

Abstract: The active control of sound transmission through a panel has been formulated using a near‐field approach. The effects of minimizing the sound power radiated by the panel and of canceling the net volume velocity of the panel are compared not only in terms of the reduction in sound radiation but also in terms of the change in the space average mean‐squared velocity of the panel and the space average mean‐squared pressure at its surface. Simulations of a thin panel excited by an incident acoustic plane wave and a piezoelectric control actuator show that volume velocity cancellation gives similar reductions in the transmitted sound power to the minimization of sound power radiation up to frequencies at which the size of the plate is about half an acoustic wavelength. The acoustic radiation is analyzed in terms of the radiation modes of the panel which are also used to explain spillover effects. Spillover, which leads to increases in the mean‐squared velocity of the panel and to increases in near‐field pressur...

Structure of Supersonic Jet Flow and Its Radiated Sound

Abstract: The present paper explores the use of large-eddy simulations as a tool for predicting noise from first principles. A high-order numerical scheme is used to perform large-eddy simulations of a supersonic jet flow with emphasis on capturing the time-dependent flow structure representating the sound source. The wavelike nature of this structure under random inflow disturbances is demonstrated. This wavelike structure is then enhanced by taking the inflow disturbances to be purely harmonic. Application of Lighthill's theory to calculate the far-field noise, with the sound source obtained from the calculated time-dependent near field, is demonstrated. Alternative approaches to coupling the near-field sound source to the far-field sound are discussed.