properties of sound

SOUND AND ITS PROPERTIES At a Glance

Introduction

Sound waves can be studied by observing its properties.

These are the distinguishing characteristics of sound.

Properties of Sound

Pitch

Intensity

Loudness

Quality

Pitch

This refers to the highness or lowness of a sound.

It is dependent on the frequency of the sound.

Note Frequency (Hz)

C 262

C# or Db

277

D 294

D# or Eb

311

E 330

F 349

F# or Gb

370

G 392

G# or Ab

415

A 440

A# or Bb

466

B 494

C’ 524

Intensity

This refers to the energy transported by a wave per unit time across a unit area perpendicular to the energy flow. (Power/Area)

It is expressed in terms of W/m2.

Human ear can detect sounds with an intensity as low as 10-12 W/m2 and as high as 1 W/m2.

Loudness

This is a subjective interpretation that varies from person to person.

It is commonly measured in terms of decibels (dB).

It is related to the following The energy of a vibrating object The condition of the air the sound wave travels

through The distance between the observer and the sound

source

Loudness

This is a subjective interpretation that varies from person to person.

It is related to the following The energy of a vibrating object The condition of the air the sound wave travels through

The distance between the observer and the sound source

Relationship between intensity and loudness

is the sound level or loudness

I is the intensity of the sound source

Io is the intensity of sound at the threshold of hearing

Intensity of Various Sound Sources

Source of the Sound

Sound Level (dB)

Intensity (W/m2)

Jet plane at 30 m 140 100

Threshold of pain 120 1

Loud rock concert 120 1

Siren at 30 m 100 1 x 10-2

Auto interior at 90 kph

75 3 x 10-5

Busy street traffic 70 1 x 10-5

Talk at 50 cm 65 3 x 10-6

Quiet radio 40 1 x 10-6

Whisper 20 1 x 10-10

Rustle of leaves 10 1 x 10-11

Threshold of hearing

0 1 x 10-12

Sample Problems on Loudness and Intensity

At a busy street corner, the sound level is 70 dB. What is the intensity of sound there?

What is the intensity of the sound at the pain level of 120 dB?

What is the sound level of a sound whose intensity is 2.0 x 10-6 W/m2.

Quality

Also known as timbre or tone color

It is the distinguishing feature of a sound.