Argosary Acoustics Innovations Glossary items.

GLOSSARY & TECHNICAL PRODUCT DESCRIPTIONS

• Acoustics--the science of sound including its production, transmission and effects

• Absorption--the properties of a material to convert sound energy into heat thereby reducing the amount of sound energy that is reflected.

• Reflection--the amount of sound reflected off a surface.

• Diffraction--for purposes of this glossary, diffraction as taken as the bending of sound waves around small obstacles or when there is a change in the properties of the medium in which the sound is traveling.

• Diffusion--the scattering of a sound wave off a surface.

• Frequency--the number of oscillations or cycles per unit of time. For sound this is expressed as Hertz (Hz) where one Hertz is equal to one cycle per second. Resonant frequency is the frequency at which resonance occurs.

• Bandwidth--a term for a measure of the range of sound frequencies in Hertz.

• Half-power Bandwidth--the location in Hertz above and below the resonant frequency where the loss is minus 3dB.

• Decibels--a dimensionless unit based on comparing the ratio of power, energy or intensity of two quantities, one of which is a designated reference. The scale is logarithmic which results in greater sound levels or loss between scalar values at high frequencies and lower sound levels or loss at the lower frequencies.

• Free Sound Field--comprised of sound waves from a source where there are no obstructions.

• Reverberant Sound Field-- comprised of sound waves that have little or no velocity or direction.

• Tuned acoustic resonator--a metal box with a perforated metal face with a filler of porous material. The edges of the holes in the perforated face plate respond to a source of sound with small displacement but violent vibrations. This pumps sound at the resonant frequency into the porous material behind where friction with the fibers of the material changes the energy into heat. The heat then dissipates.

• The Veil Phenomenon--occurs specifically with the Veil panel when diffraction through the holes of the perforated top (or bottom) propagates new secondary waves. These new wavelets add to, or cancel each other with the sum determined by their phases and amplitudes. Thus the amplitude and strength of the new wave front can be as low as 0 or almost as high as the sum total.

• Wavelength--a wave of compression and refraction produced by sound passing through air A wavelength is the distance between two identical positions in the cycle and varies with frequency; longer wavelengths at low frequency at, short wavelengths at high frequency.

• Octaves and Octave Bands--an octave is a tone whose frequency is twice the given tone. Octave bands are commonly divided into 10 divisions: 31.5, 63, 125, 250, 500, 1000, 2000, 4000 Hz and so on. 1/3 octave bands are further divided into 1/3 of the above.