Ultrasonics Applications for Industry and Research, On and Off Planet Earth.

Attenuation of Sound in Air

The attenuation of ultrasound in air at standard temperature and pressure is an important consideration in the placement and use of air coupled ultrasonic transducers.  To a good approximation, the attenuation in air is given by

where is the frequency expressed in MHz.  For example, at 1MHz the attenuation of sound in air is approximately 12/7 db/cm or 1.7 dB/cm.  Therefore 1MHz transducers placed 10cm apart would loose 17dB due to the air column.  The exact frequency dependence of attenuation must also include corrections for pressure, temperature and humidity.

 This relationship was determined spectroscopically using the SIA-7:

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Last modified: April 02, 2007