Sound and Microphone

Prepared by:Shubhanshu Pathak

2015-2016 July Batch

SoundSound is a vibration that propagates as a

typically audible mechanical wave.Sound travels at a speed of 334 m/s.

Physics of Sound Sound travels in a Medium.Sound waves are generated by a sound source

such as vibrating diaphragm of a speaker.

Components of Sound Wave

WavelengthAmplitude Velocity

Components(contd.)EnvelopePhasingHarmonicsFrequency

Types of Sound WavesLongitudinal wavesTransverse wavesStationary waves.

OctaveRange of audible frequency is divided into

audio band.Octave is the interval between any 2

frequencies having tonal ratio of 2:1.There are 3 Octaves:

Octave(contd.)Bass: Consists of 4 octaves and is divided into

2 groups.Mid: Consists of 4 octaves and is divided into

2 groups.Treble: Consists of 2 octaves.

MicrophoneA microphone is a transducer that converts

sound into an electrical signal.First proper microphone was developed by

David Hughes, in the US in, 1877.

ComponentsCapsule: The transducing element.Diaphragm: The moving film.Housing: Brings signal from element to other

equipments.

Polar PatternThree prominent polar patterns are:1. Omnidirectional.

Polar Pattern(contd.)2.Bidirectional(Figure of eight)3.Directional(Cardioid).

TypesCondenser microphone: The were invented at bell labs.They work on the principle of variable

capacitance.

Moving coil MicrophoneThey work on the principle of electromagnetic

induction.The sound is produced by the motion of the

coil.

Ribbon MicrophoneThey work on pressure difference.A thin aluminium foil motion produces voltage

which a transformer boosts.They are used for percussion instruments.

PropertiesFrequency response.Overload limit.Maximum SPL.Sensitivity.Self Noise.Signal to Noise ratio.Proximity effect.

Sennheiser MD421Glass composite housing and hardened

stainless steel basket.Frequency response 30Hz-17kHzEffective feedback rejectionClear sound reproduction.

ConclusionMicrophone are of great importance for audio

industry.

Proper care is to be taken in selection and handling of a microphone.