principles and physics of sound

8/22/2019 Principles and physics of sound

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SOUND

Introduction

Physics of Sound

Characteristics of sound Human perception of sound


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INTRODUCTION

What is sound ?

Sound is

A form of energy made by vibrations.

When an object vibrates it causes the air particlesaround it to move.

These particles bump into particles close to themand this continues until they run out of energy.


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INTRODUCTION

How does sound travel ?

Sound travels in forms of waves:

Longitudinal waves

Transverse waves


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SOUND NEEDS MEDIUM

GasesMost of the soundswe hear travel

through gases, suchas air.

Sound waves travelslowly through the

air.

For example: Soundfrom a bell, a horn,or an alarm clock

travels through theair.

LiquidsSome sounds thatwe hear travel

through water.

Sound waves travela faster through

water than throughthe air.

Sonar is the way to

use sounds to locateobjects underwater.

What animals usesonar?

SolidsSome sounds thatwe hear travelthrough solids.

Sound waves travelvery fast throughsolids.

For example: Whenyou hit a drum, itvibrates, then thesound travelsthrough the air, toyour ears.


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PHYSICS OF SOUND

Medium velocity m/sec

air (20 C) 343

air (0 C) 331

water (25 C) 1493sea water 1533

diamond 12000

iron 5130

copper 3560

glass 5640

SPEED OF SOUND IN VARIOUS MEDIUMS :


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Longitudinal Wave

wave particles vibrate back and forth along thepath such that the wave travels.

Also called Compressional Wave

INTRODUCTION


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Transverse waveswave particles vibrate in an up-and-down motion.

INTRODUCTION

Crests Highest part of a wave

Troughs The low points of the wave


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PHYSICS OF SOUND

WAVELENGTH :

THE MINIMUM DISTANCE IN WHICH SOUND WAVE REPEATS ITSELF IS

CALLED WAVELENGTH.

OR

THE DISTANCE BETWEEN THE TWO CONSECUTIVE CREST OR TROUGHS ISCALLED WAVELENGTH.

WAVELENGTH


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PHYSICS OF SOUND

AMPLITUIDE :

THE MAXIMUM DISPLACEMENT OF THE PARTICLE OF THE MEDIUM FROM

THEIR ORIGINAL UNDISTURBED POSITIONS, WHEN THE WAVE PASSESTHROUGH THE MEDIUM, IS CALLED AMPLITUIDE OF THE WAVE.

AMPLITUIDE


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PHYSICS OF SOUND

TIME PERIOD :

THE TIME REQUIRED TO PRODUCE ONE COMPLETE WAVE OR CYCLE.

OR

TIME TAKEN TO COMPLETE ONE COMPLETE VIBERATION

TIME PERIOD


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PHYSICS OF SOUND

FREQUENCY :

THE NUMBER OF COMPLETE WAVES PRODUCED IN ONE SECOND.

OR

NUMBER OF VBERATIONS PER SECOND.

Unit is Hertz (Hz)


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PHYSICS OF SOUND

VELOCITY OF WAVE :

THE DISTANCE TRAVELED BY THE WAVE IN ONE SECOND

VELOCITY = DISTANCE TRAVELED

TIME TAKEN


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PROPOGATION OF SOUND IN SPACE


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CHARACTERISTICS OF SOUND

LOUDNESS :

IT IS THE MEASURE OF SOUND ENERGY REACHING THE EAR PER SECOND.

LOUDNESS DEPENDS UPON THE AMPLITUIDE OF SOUND WAVE.

IT IS MEASURED IN DECIBLE (Db)


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SOUND

Decibel scale


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PITCH:IT IS THAT PROPERTY OF SOUND BY WHICH WE CAN

DISTINGUSH BETWEEN DIFFERENT SOUNDS OF THE

SAME LOUDNESS.

IT DEPENDS UPON THE FREQUENCY OF VIBERATION.


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HUMAN EAR

Sound Waves

Sound waves are sent.

The outer ear catches the sound waves.

The middle ear takes the sound waves and vibrates the

eardrum.

The inner ear sends the messages to the brain.

Middle Ear

Inner Ear

Outer Ear


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HUMAN EAR

RANGE OF HEARING IS 20 TO 20,000 Hz.


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SOUND

ULTRASOUND

- sound waves with frequencies above the

normal human range of hearing.Sounds in the range from 20-100kHz

INFRASOUND

- sounds with frequencies below the

normal human range of hearing.

Sounds in the 20-200 Hz range


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HEARING RANGE OF ANIMALS

principles and physics of sound

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