We are still talking here about “Bell telephone laboratories”. Bell engineers needed a reliable metric to develop their new telephone devices. So they created the decibel, or one tenth of a Bel – named in honor of their venerable boss, Alexander Graham Bell.

Decibels Learn more →


dB & dBA

In 1933, Harvey Fletcher and W. A. ​​Munson from Bell Telephone Laboratories presented loudness level contours (curves of equal perception of a sound). These curves were obtained statistically following listening tests carried out using listeners with hearing considered to be normal.

dB & dBA Learn more →

Earing and sound

Earing & Sounds

Sounds are defined as an auditory sensation generated by an acoustic wave (Larousse). This definition introduces two notions: acoustic waves and human hearing. When an acoustic wave reaches the head of a listener, it is picked up by the pinna and directed toward the ear canal. These two elements form the outer ear.

Earing & Sounds Learn more →


Sound Waves

A sound wave is a pressure disturbance that propagates through the air. This disturbance can be caused by a vibration (for example the vibrations of the vocal cords) or even turbulence in an air flow, such as a whistle.

Sound Waves Learn more →

Speed Profile

Static Thermal Permeability

The static thermal permeability is the low frequency limit of the dynamic thermal permeability. The thermal permeability problem is the thermal analogy of the viscous permeability problem. When the frame of a porous medium has a sufficient thermal capacity for the compressibility to reach its isothermal value at low frequencies, the excess acoustical temperature can be considered to vanish at the pore walls (this replaces the no-slip condition for viscous flow) and a static “thermal permeability” exists.

Static Thermal Permeability Learn more →

Poisson's Ratio

Young’s Modulus, Poisson’s Ratio and Loss Factor

For isotropic poroelastic materials, the elastic properties to be characterized are Young’s modulus (E), Poisson’s ratio (v) and loss factor (η). The method is based on the dynamic compression of two samples of different shape factors (s1 and s2). This enables the simultaneous characterization of the three elastic properties. The method is valid for frequencies from 20 to 100 Hz.

Young’s Modulus, Poisson’s Ratio and Loss Factor Learn more →

Scroll to Top