2. Nature of Sound
• Sound is a longitudinal wave motion
consisting of a train of Compression and
rarefaction travelling in a medium. When
these waves strike the eardrum these are
converted into signals which are carried to
the brain by the auditory nerves and are
finally interpreted into what we call Sound.

3. SOUND WAVESOUND WAVE
MOLECULESMOLECULES
1.2. Soundwaves
Source
of
Sound
Region of High Pressure (Compression) and
Region of low pressure (Rarefaction)

4. Pressure and intensity of
Sound waves
• Sound waves produce variation of pressure
in the medium in the form of compressions
and rarefactions in quick successions.
Sound pressure variation is therefore
represented by newton per square metre
(N/m2
), or pascal (Pa). In terms of micro-
bar (dyne per Sq cm) one Pa is equal to ten
micro-bars.

5. Sound & Sensitivity of
human-ear:
• Human ear is very sensitive to sound
intensity & can detect sound as
low as 0.1 pW/m2
(or 10 dB below the
threshold of hearing).
• The ear cannot distinguish difference of
intensity of less than 1 dB between two
sounds.

6. • Minimum level which can be comfortably
detected over threshold of hearing is 3 db
for speech or music.
• The ear possesses characteristics of
masking that is the louder sound reaching
the ear can suppress the weaker sound.
• The ear judges’ direction of sound from the
first received even if it is weaker.

7. Electrical Representation

8. COMPONENTS OF SOUND IN AN ENCLOSED
SPACE
- Direct Sound
- Reflected Sound

9. Loudness & Phon
• Loudness is defined as the intensity of
sound as judged by the ear. It needs higher
intensity at low frequencies than at high
frequencies to impart same sensation of
loudness.
• The intensity of 60 dB at 40 Hz and of 0 dB
at 1000 Hz imparts the same loudness.

10. Phon :The intensity in dB with reference to
Threshold of hearing as perceived by the
ear at 1000 Hz is called phon (P). If it is 0
dB then loudness is 0 phon, if it is 40 dB
then loudness is 40 phon.

11. Sone: It is found that a 10 dB increase in
sound level corresponds approximately to a
perceived doubling of loudness. One sone is
defined as the loudness expressed by a
person listening to a 1000 Hz tone of 40
phon loudness level. Similarly 50 phons
would have a loudness of 2 sones, 60 phons
would be 4 sones, etc. The relation
between sone (L) and Phon (P) is given by-
10logL= (P - 40) log2

12. Frequency
Fletcher-Munson Curves for loudness vs. Frequency

13. Frequency range for Speech
Audible frequencies range from 16Hz to
20000 Hz. For satisfactory transmission of
speech two factors are very important.
• Intelligibility- It is defined as the
clearness of one’s speech determined
through the test of articulation.
• Energy-The energy in speech is contained
mostly in the low frequencies.

14. Overtones and Timbre
• Sound waves produced by Speech and
musical instruments are not pure sine
waves, but are complex waves consisting
not only the fundamental frequencies
(tones) but also of their harmonics, and
other frequencies, called ‘overtones’. The
proportion of tones & overtones present in
the sound that helps us to identify any
particular voice is called Timbre.

15. • Intervals: It is defined as the ratio of two
frequencies.
Example-Interval of 400Hz &100Hz is 4.
• Octaves: An interval of 1:2is called an
OCTAVE.
Example: One octave of 200 Hz is400 Hz
• Harmonics: It is an integer ratio between
two frequencies.
Example: 2nd
harmonicof 100Hz is 200Hz

16. Pitch
It generally represents the perceived
fundamental frequency of a sound. Sound
waves with a longer wavelength don't
arrive at the ear, as often (frequently) as the
shorter waves. The shorter the wavelength,
the higher the frequency, and the higher the
pitch, of the sound. In other words, short
waves sound high; long waves sound low.

18. Acoustic Reverberation
• The term acoustics has been derived from
the Greek word akoustos, meaning
“hearing.” It is the area of science devoted
to the study of the production, transmission,
reception, and effect of sound.
• In the field of broadcasting the broadcast
studios are the originating place of the
program to be broadcast live, or recorded
for future use. Hence proper care should be
taken in their designing and construction.

19. Reverberation
• The persistence of sound, caused due to
repeated reflection is called reverberation.
• In an studio the sound is received directly
from the source as well as sound reflected
from walls, floor, ceiling, etc. The sound
persists for a noticeable time even after the
original sound stops. It fades away
gradually.

20. Microphone
Microphone is a transducer.It converts sound wave
(acoustical energy) into electrical energy
Five important characteristics of microphone
• Operating principle
• Frequency response
• Directionality of microphone
• Electrical output and
• Physical design of the microphone

21. Microphones
• Acoustical classification
• Electrical classification
• Polar pattern-wise classification

23. Pressure-operated Microphones
• Sound pressure is applied on
one side of the diaphragm.
• Electrical output is
proportional to the sound
pressure.
• Theoretically omnidirectional.
• However,the physical size of
microphone works as an
obstacle at high frequency.
• Sensitivity at HF decreases.
Operating Principle

24. Pressure-operated Microphones-cont’d
• Examples-Moving Coil,
Carbon, Crystal and
Condenser Microphones
Typical Polar Pattern

25. Pressure Gradient(velocity)
Operated Microphones
• Both sides of the
diaphragm are
exposed to the sound
pressure.
• Hence, the electrical
output is proportional
to the difference in
pressure on the two
sides.
Operating Principle

26. Combined-operation
Microphones
• The principle of pressure-
operated microphones and
pressure gradient operated
microphones are combined
to get maximum sensitivity
in one direction and
minimum sensitivity in the
opposite direction.
• Unidirectional
characteristics. An Acoustic Labyrinth

28. Electrodynamic Microphone with
Moving Coil
• A dense coil of wire
moves within a strong
electromagnetic field.
• Induced current is
proportional to
displacement velocity.
• Great mechanical
robustness.
.
Operating Principle

29. Electrodynamic Microphone with
Moving Coil - cont’d
• The dense coil of wire makes it
less sensitive especially to very
soft sounds or high pitch sounds
(sibilants or harmonics).
• Used in live performance where
rough handling is common.
• Examples- AKG D-202, D-222,
D-900, D-770, D-190E, SM58,
SM57, SM48 etc.
AKG D-770
Instrument/Vocal
Microphone

30. Electrodynamic Ribbon
Microphone
• The coil of moving coil
microphone is replaced by
a corrugated thin strip of
aluminium.
• Very sensitive to shock
and large sound volumes.
• Very delicate.
• Unusable in windy
condition.
Operating Principle

31. Electrodynamic Ribbon
Microphone- cont’d
• Very low impedance and
hence uses in-built
transformer.
• Inherently bidirectional.

32. Electrostatic(Condenser)
Microphones(single diaphragm)
• A thick metallic plate as a
diaphragm is fixed to a
perforated metal back plate.
• Electrical charge is applied
to either or both plates.
• Sounds pressure changes
the distance between two
plates and causes variation
in the capacitance.
• Requires in-built pre-amp Operating Principle

33. Electrostatic(Condenser)
Microphones(single diaphragm)-cont’d
• High sensitivity and very good frequency response.
• Smaller and lighter diaphragm gives more accurate
and pin-sharp sound.
• Requires external power supply popularly known as
“Phantom Power Supply” - 9v to 52v.
• Very sensitive to humidity and temperature.
• Less sensitive to shock.
• High cost.

34. Electrostatic(Condenser)
Microphones(single diaphragm)-cont’d
• Tends to record sound as it
really is.
• Large diaphragm gives flattering
response.
• Resonant frequency at the upper
end of audio spectrum.
• Examples- C2000B, C3000B,
SM86, SM94, SM81 etc.
SHURE
SM94
Instrument Mic.

35. Electret Microphone
• It is a modified form of
condenser microphone.
• It does not use external
power supply.
• Either diaphragm or back-
plate is permanently
charged.
• However, pre-amp requires
power supply.
Electret

36. Electret Microphone- cont’d
• The output is independent of the diaphragm
surface area.
• Light and small in size.
• Excellent quality/price ratio.
• However, not suitable for bass.

38. Omnidirectional Microphones
• Gain remains constant in
all directions-It is unity.
• However, true Omni is
possible at low frequency
only.
• Moving coil and Condenser
microphones are designed
to work as omnidirectional
microphones.
Omnidirectional

39. Omnidirectional Microphones-cont’d
• Pickup angle-360 degree.
• No proximity effect.
• Used for recording ambient
and background sound and
also for vocals.
• Examples- C4000B,
C414B, C577WR, D230
• C4000B has dual large
diaphragm.

40. Bi-directional Microphones
• Figure of 8 pattern.
• Gain is proportional to cosine
of angle of incident of sound.
• Pickup angle-90 degree(120
degree at -6dB)
• Limited use.
• Example- Ribbon Microphone,
Condenser Microphone

41. Cardioid Microphones
• Gain= 1+cosine of angle of
incident of sound.
• Heart -shaped.
• Pickup angle(Coverage angle) -
130 degree.(180 degree at
-6dB)
• Null angle - 180 degree.
• Degenerates towards omni
(Hypocardioid) at low frequency.
Cardioid

42. Cardioid Microphones- cont’d
• More directional than
required at high frequency.
• Favoured for stage use as it
prevents feedback.
• Examples- AKG D770,
C3000B, C2000B etc.

43. Hypercardioid Microphones
• Gain= 0.5+cosine of angle of incident
of sound.
• Cardioid +Bidirectional
• Pickup angle - 105 degree.(140
degree at -6dB)
• Null angle - 110 degree.
• Narrower pick-up than cardioid,
hence feedback rejection improves
even further.
• The least overall pickup of ambient
sound.
• Examples- C1000S, D660S
hypercardioid

44. Supercardioid Microphones
• Pickup angle - 115 degree.
• Null angle - 125 degree.
• Maximum ratio of on-axis
pickup to ambient pickup.
• Useful for more distant
pickup or in higher ambient
noise level.
• Examples- D880/D880S,
Beta58A, Beta87A etc.

45. Unidirectional Microphones
• The term is used for ‘Gun’
microphone.
• Long and rod shaped.
• Good for recording single
voice in noisy locations.
• Also used for picking up
voice from long distance.
• Shotgun(18 in. long), Long
gun(36 in. long).
• Long gun pick-up-20 to 25
feet.
• Example- D900.
s
GUN MICROPHONE

46. Electrodynamic Microphone for recording of
voice in hand held condition
Uses • Recording of interview of players and sports
authority.
• Less sensitive so suitable for noisy situation
• Mechanically strong and robust Examples- AKG D-202,
D-222, D-900, D-770, D-190E, SM58, SM57, SM48
SHURE
SM58
Vocal
Microphone
AKG
D190E
Speech/Instrument
Microphone

47. Condenser Microphone
Uses
• Tends to record sound as
it really is.
• Broad Frequency
spectrum.
• Uses to record when
sound source is not near
• Examples- C2000B,
C3000B, SM86, SM94,
SM81 etc
SHURE
SM81

49. Lip Microphone
• A close talking microphone.
• Designed to ensure constant
spacing between the
microphone body and the lips
of the user.
• Also known as noise canceling
microphone
• Similar to ribbon microphone.
• Used for radio reporting and
sports commentary.
Lip Microphone

50. Gun Microphones
• Highly unidirectional
• Long and rod shaped.
• Good for recording single
voice in noisy locations.
• Good for recording sound
effect from a far distance.
• Also used for picking up
voice from long distance.
• Shotgun(18 in. long), Long
gun(36 in. long).
• Long gun pick-up-20 to 25
feet.
• Example- D900.
GUN MICROPHONE

51. Lapel Microphones
• It is usually electret
microphone.
• Based on Lavalier Technology.
• Omni directional polar pattern.
• Very small and light- weight.
• Offers reasonable intelligibility
in fairly noisy surrounding.
• High frequency loss when
hidden behind clothing.
Lapel Microphone

52. Lapel Microphones-cont’d
• Also called as neck microphone.
• May be corded or cordless.
• Worn at the chest or clipped to clothing.
• It can be powered by batteries or phantom power.
• Suitable for running commentary or a lecture.
• Can also be used for wind instrument.

53. Parabolic Microphone
• A cardioid microphone is
placed at the focal point of a
parabolic reflector.
• The parabolic reflector is made
of sheet metal or stratified
polyester or glass fibre.
• Low frequency pickup is
proportional to the diameter of
the reflector.
• Used for recording faint sounds
such as birdsong.
Operating principle

54. Boundary Microphone
• A small capsule microphone
usually an electret, is housed
in a flat receptacle.
• The flat receptacle works as
a plane reflective surface.
• The directivity is
hemispherical at all
frequencies.
• More dynamic range and
clarity.Omnidirectional.
• Also known as PZM.
Pressure Zone Microphone

55. Contact Microphone
• Size is small.
• Attached with the
sound source itself.
• Pickup vibration
pulsing through
solid.
• Attach to a point so
that it should not
come in the view of
camera.
• HF response is
good but LF
response is bad.

56. Wireless Microphones
• These are ordinary
microphones with an FM
transmitter.
• Provides complete freedom
of movement.
• Lapel type or handheld.
• Omnidirectional.
• Interference from outside
source.
• Suitable for stage
performance.
• Suitable for places where
laying of microphone cable
is not possible
SHURE MICROPHONE
Lapel Mic
Transmitter
Receiver
Handheld
Mic.

57. Placement of Microphones
• Placement of microphones depends on the acoustic
nature of the sound source and the acoustic
characteristics of the microphones.
• Always use minimum number of microphones.
• Microphone should be placed with its 0 axis facing
the source of sound to avoid off axis colouration.
• When two or more microphones are used, it should
be ensured that their outputs are in phase.
• The Microphone should not be too close or too far
to the sound source.

58. Placement of Microphones-cont’d
• When the Microphone is close to the sound source,
direct sound is predominant and hence the output
appears to be ‘dry’. When it is far away from the
sound source, the reverberant (indirect) sound is
predominant and hence the output lacks in clarity.
• Microphone should not be placed very close to a
reflecting surface like bare walls, hard tables etc.
• Directional microphones should not be placed too
close to the source of sound to avoid boosting of
low frequencies due to a phenomenon called
proximity effect.

59. Placement of Microphones-cont’d
This effect should be normally avoided by placing
the microphones fairly away (30-45 cm) from the
source of sound.
• For spoken word recordings, microphones should
not be placed directly in line with the mouth since it
will result in ‘p’ blasting.
• A talker should not hold the script between his face
and the microphone otherwise shadowing effect will
occur at high frequencies.

60. Placement of Microphones-cont’d
• For stringed instruments (violin,sitar,sarangi,etc.) 0
axis of the microphone should be preferably placed
normal to the front face of the instrument.
• For instrument with large sound output (like drums
and other percussion and bass instrument) the
microphone should be placed well away from the
source of sound.
• For wood wind instrument where the instrument is
not particularly direction (such as flute) the
microphone may be placed about 60 cm.away .

61. Placement of Microphones-cont’d
• In outdoor locations because of the higher ambient
noise level, the working distance must be kept less
than the corresponding distance when working
indoors.
• When using multiple microphones, to reduce
acoustic interference between the microphones
THREE-to-ONE rule should be followed, which
states that the microphone-to- microphone distance
should be at least three times the source-to-
microphone distance.

62. Placement of Microphones
• Microphone
should be placed
with its 0 axis
facing the source
of sound to avoid
off axis effect.
• The Microphone
should not be too
close or too far to
the sound source.