1.3 Introduction
1.3.1 Characteristics of Sound - Pressure Variations
1.3.2 Characteristics of Sound - Speed of Sound
1.3,3 Characteristics of Sound - Pitch Loudness and Timbre
1.3.4 Characteristics of Sound - Intensity
1.3.5 Doppler Effect
Unit 2.1 Multiple Choice Extended Questions - Waves
Unit 2.1 Multiple Choice Extended Answers-Waves
Unit 1.3 Multiple Choice Questions - Sound
Unit 1.3 Multiple Choice Answers - Sound

Unit 1.3 Sound Waves


The intensity of a periodic sound wave, which is the power per unit area, is

I = [Poweravg] /A

The sound level of a sound wave in decibels is

β = 10 log [I/Io]

The constant Io is the threshold of hearing (1.00 X 10-12 Wm-2), and I is the intensity (power) of the sound wave in watts per square meter.

Sound waves are longitudinal and travel through a compressible medium with a speed that depends on the elastic and inertial properties of that medium. The speed of sound in a gas having a bulk modulus B and density ρ is √[B/ρ]

The pressure wave is π/2 or (90°) out of phase with the displacement wave.

The change in frequency heard by an observer whenever there is relative motion between a source of sound waves and the observer is called the Doppler effect.

The observed frequency is f' = f {[Vsnd ± Vo]/[Vsnd ± Vs]}

In this expression, the signs for the values substituted for Vo and Vs depend on the direction of the velocity.

— positive value if the velocity of one is toward the other

— negative value if velocity of one is away from the other.

Concept by Kishore Lal. Programmed by Kishore Lal... Copyright © 2015 Kishore Lal. All rights reserved.