Question

A siren is to operate at 500 Hz in air and at a small height above the ground. Assuming hemispherical divergence and no absorption (or reflection) by the ground, what is the absorptive loss coefficient and what must be the acoustic output of the siren in watts if it is to produce an intensity level of 60 dB re µ Pa at a distance of 1000 ft for each of the following conditions:

(a) no absorption by the air.
(b) according to the classical absorption coefficient.
(c) completely dry air.
(d) air of very high relative humidity.

Answer 1

To determine the absorptive loss coefficient and acoustic output of the siren, we need to calculate the sound intensity level at a distance of 1000 ft for different conditions.

Step-by-step explanation:

Before we can determine the absorptive loss coefficient and the acoustic output of the siren, we need to calculate the sound intensity level at a distance of 1000 ft for each of the given conditions.

(a) No absorption by the air: We can use the inverse square law to calculate the intensity level. Since there is no absorption, the intensity remains constant at all distances.

(b) According to the classical absorption coefficient: We need to determine the classical absorption coefficient for the given frequency and conditions. Then, using the absorption coefficient, we can calculate the intensity level.

(c) Completely dry air: In this case, we need to calculate the absorption coefficient for dry air. Using the absorption coefficient, we can determine the intensity level.

(d) Air of very high relative humidity: For this condition, we need to calculate the absorption coefficient for air with high relative humidity and then determine the intensity level.