Question

4-2. A plane sound wave in water at 20°C (68 F) has a sound pressure level for the incident wave of 105 dB and a frequency of 1000 Hz. The wave is normally incident on a very thick concrete wall. Determine [A] the transmission loss, dB: [B] the intensity of the incident wave and the intensity of the transmitted wave, and [C] the sound pressure level of the transmitted wave.

Answer 1

Given Data:

The sound pressure level is,

The temperature of the water is,

Part (A):

From the graph of transmission loss v/s frequency, the transmission loss at 1000 Hz is given as,

Part (B):

The expression for the intensity of the incident wave is,

Here, I is the intensity of the incident wave, and I₀ is the threshold intensity of human.

Substitute the values in equation (1)

The expression for the intensity of the transmitted wave is,

Substitute the values in equation (2)

Therefore, the intensity of the incident wave and the transmitted wave is 0.0316 W/m² and 9.99x10^-8 W/m².

Part (C):

The sound pressure level of the transmitted wave is calculated as,