The Science of Sound: How It Works

Sonozorb works by converting sound waves into thermal energy. Waves enter the porous material and bounce off the microscopic fibers. With each bounce, the sound wave loses energy. The curved surface of the fiber also serves to disperse the energy in multiple directions, further diluting the waves energy.


How Sound is Transmitted

Sound Waves
Sound is transmitted in the form of sound waves, which are a series of pressure variations. Sound waves are characterized by the generic properties of waves, which are frequency (hertz or Hz), wavelength (inverse of frequency), period, amplitude (commonly dB or decibel), intensity, speed, and direction.

Properties and Criteria for Sound Absorption

When sound is absorbed, the wave is converted into thermal energy. Absorption of a given material is frequency-dependent and is affected by the size, shape, location, and mounting method used. A good sound absorber is normally a porous material. The ability to absorb a given sound is expressed by a Sound Absorption Coefficient. This coefficient varies from zero to one – the higher the coefficient the more effective the absorption.

Human perception of Sound

Human Perception

For humans, hearing is limited to frequencies between about 20 Hz and 20,000 Hz (20 kHz). Higher frequencies are generally perceived with greater intensity up to about 8,000 Hz (8 kHz) and then decrease again. In other words, a 60 dB sound at 40 Hz may be barely noticeable, while a 60 dB sound at 2,000 Hz would be very noticeable.

Common Frequencies

In automotive applications, common unwanted noise have a variety of frequencies, depending on the source. The chart at right shows general frequency ranges of noise from various sources.

Fiber Diameter Effects

A smaller fiber diameter results in better absorption, especially in the middle and higher range frequencies. A 50% reduction of fiber diameter results in a four fold increase in flow resistivity. Sonozorb has a fiber diameter generally 3 to 30 times smaller than comparable synthetic acoustic insulations.

Material Thickness and Density Effects

Generally the thicker the insulating material, the more effective the absorption. Material that is more dense will also achieve better absorption performance.