Sound & RecordingSound & Recording

Ears, Physics, Acoustics, Ears, Physics, Acoustics, Microphones and Digital Microphones and Digital

RecordingRecording

EARSEARS

Difference between Hearing and Vision.Difference between Hearing and Vision. Ear safety.Ear safety. Ear training.Ear training.

Hearing vs. VisionHearing vs. Vision

Difference between Hearing and Vision.Difference between Hearing and Vision. Hearing is omnidirectional, vision is Hearing is omnidirectional, vision is

directional.directional.• You can hear perceive sound emanating from You can hear perceive sound emanating from

behind your head.behind your head.• You can only see what you are looking at directly.You can only see what you are looking at directly.

Sound can be layered, vision can not.Sound can be layered, vision can not.• To a bass line, you can add drums, vocals, guitar, To a bass line, you can add drums, vocals, guitar,

etc. and still hear it all.etc. and still hear it all.• If I walk in front of you, you won’t be seen If I walk in front of you, you won’t be seen

anymore.anymore.

Natural Ear ProtectionNatural Ear Protection

Ossicles (three bones) in middle ear adjust Ossicles (three bones) in middle ear adjust to protect inner ear from extreme to protect inner ear from extreme pressure.pressure. Takes 1/10Takes 1/10thth of a second for ossicles to adjust. of a second for ossicles to adjust. No protection against sudden loud sounds.No protection against sudden loud sounds. Can not adjust enough to deal with extremely Can not adjust enough to deal with extremely

loud sound.loud sound.

Hearing DamageHearing Damage

Continued exposure to high sound-Continued exposure to high sound-pressure levels (SPLs) damages receptive pressure levels (SPLs) damages receptive fibers in cochlea.fibers in cochlea. Mid-high frequencies go first – important for Mid-high frequencies go first – important for

understanding speech.understanding speech. Cotton ears: Temporary Threshold Shift Cotton ears: Temporary Threshold Shift

(TTS). Ears shut down to protect themselves.(TTS). Ears shut down to protect themselves. Ringing ears: Tinnitus. Sign of possible Ringing ears: Tinnitus. Sign of possible

permanent damage.permanent damage. Hearing loss affects 1 in 9. Progressive.Hearing loss affects 1 in 9. Progressive.

Physiological DamagePhysiological Damage

Loud sounds cause adverse physiological Loud sounds cause adverse physiological effects:effects: Increases heart rate.Increases heart rate. Raises blood pressure.Raises blood pressure. Contracts blood vessels and muscles.Contracts blood vessels and muscles. Releases stress hormones.Releases stress hormones. Disrupts digestive functions.Disrupts digestive functions. Causes anxiety and fatigue.Causes anxiety and fatigue.

Ear TrainingEar Training

Paying attention to sound:Paying attention to sound: Layers – selective listening.Layers – selective listening. Content.Content. Function.Function. DirectionDirection CharacteristicsCharacteristics

Physics and PsychophysicsPhysics and Psychophysics

Sound waves.Sound waves. Frequency.Frequency. Amplitude.Amplitude. Timbre.Timbre. Envelope.Envelope.

Sound WavesSound Waves

Created by object vibrating in an elastic Created by object vibrating in an elastic medium - causing changes in pressure medium - causing changes in pressure (number of molecules bunched together).(number of molecules bunched together). Outward movement – compression.Outward movement – compression. Inward movement – rarefaction.Inward movement – rarefaction.

FrequencyFrequency

Number of cycles Number of cycles (compression/rarefaction) per second.(compression/rarefaction) per second. Expressed in Hertz (Hz) and Kilohertz (kHz).Expressed in Hertz (Hz) and Kilohertz (kHz). Higher frequency – higher pitch.Higher frequency – higher pitch.

• Bass: 20-320 Hz.Bass: 20-320 Hz.• Mid-range: 320-5,120 Hz.Mid-range: 320-5,120 Hz.• Treble: 5,120-20,000 Hz.Treble: 5,120-20,000 Hz.• Extreme highs and lows are “sensed,” not heard.Extreme highs and lows are “sensed,” not heard.

AmplitudeAmplitude

Number of molecules in motion – higher pressure, higher Number of molecules in motion – higher pressure, higher volume.volume.

Measured in decibels (dB).Measured in decibels (dB).• 20 dB – whisper.20 dB – whisper.• 60 dB – talking.60 dB – talking.• 80 dB – yelling.80 dB – yelling.

Equal Loudness Principle.Equal Loudness Principle. Human ear is more responsive to midrange than bass and Human ear is more responsive to midrange than bass and

treble.treble. At higher levels, bass and treble need boost to sound the same.At higher levels, bass and treble need boost to sound the same.

Masking.Masking. Louder sounds mask softer sounds.Louder sounds mask softer sounds. Taken advantage of in audio compression – perceptual noise Taken advantage of in audio compression – perceptual noise

shaping.shaping.

TimbreTimbre

Gives tonal quality – difference between Gives tonal quality – difference between instruments or voices.instruments or voices. Fundamental (pure) tone – Doesn’t exist in Fundamental (pure) tone – Doesn’t exist in

nature.nature. Overtones – other tones riding along with Overtones – other tones riding along with

pure tone.pure tone.• Harmonics: exact multiples of fundamental tone Harmonics: exact multiples of fundamental tone

(For example: 4, 6, 8, 10 kHz are harmonics of 2 (For example: 4, 6, 8, 10 kHz are harmonics of 2 kHz).kHz).

• Other overtones – non-harmonic.Other overtones – non-harmonic.

EnvelopeEnvelope

AttackAttack Amount of time it takes a tone to reach maximum Amount of time it takes a tone to reach maximum

volume.volume. DecayDecay

Amount of time it takes a tone to decrease from max Amount of time it takes a tone to decrease from max to sustained volume.to sustained volume.

SustainSustain Amount of time a tone stays at a constant volume.Amount of time a tone stays at a constant volume.

ReleaseRelease Amount of time it takes for a tone to end.Amount of time it takes for a tone to end.

AcousticsAcoustics

Reflections.Reflections. Acoustic choices.Acoustic choices. Noise.Noise.

ReflectionsReflections

Direct sound.Direct sound. Sound waves coming directly off of sound source.Sound waves coming directly off of sound source.

Reflections – off of other objects, walls, etc.Reflections – off of other objects, walls, etc. Early reflections.Early reflections.

• Increase loudness – give impression of size of environment.Increase loudness – give impression of size of environment. Later reflections.Later reflections.

• Echo – distinct, single reflection.Echo – distinct, single reflection.• Reverb – reflections of reflections – flutter echos.Reverb – reflections of reflections – flutter echos.

Room shapes and materials.Room shapes and materials. Consistently shaped rooms can cause unwanted effects.Consistently shaped rooms can cause unwanted effects. Complex shapes disperse reflections more effectively.Complex shapes disperse reflections more effectively. Materials such as carpet and concrete absorb and reflect sound Materials such as carpet and concrete absorb and reflect sound

differently.differently.

Acoustic ChoicesAcoustic Choices

So what kind of space is best to record in?So what kind of space is best to record in? Depends on what you’re recording.Depends on what you’re recording.

• Orchestral is good with reverb, combining various Orchestral is good with reverb, combining various instruments on the sonic palette – live or wet room.instruments on the sonic palette – live or wet room.

• Rock needs less reverb to hear specific Rock needs less reverb to hear specific instruments more distinctly – medium room.instruments more distinctly – medium room.

• Vocal needs little reverb – dead or dry room.Vocal needs little reverb – dead or dry room.• But there is no hard and fast rule – it’s a matter of But there is no hard and fast rule – it’s a matter of

taste.taste.• Reverberation can be added in postproduction with Reverberation can be added in postproduction with

signal processing – but may not be as rich.signal processing – but may not be as rich.

NoiseNoise

Noise is everywhere.Noise is everywhere. If it’s quiet enough we can even hear our own If it’s quiet enough we can even hear our own

blood flowing through our veins – so we never blood flowing through our veins – so we never can really hear complete silence.can really hear complete silence.

Unwanted noise can be minimized with Unwanted noise can be minimized with isolation.isolation.• Keeps unwanted sounds from getting in.Keeps unwanted sounds from getting in.• Stops loud noises from disturbing others.Stops loud noises from disturbing others.

MicrophonesMicrophones

TypesTypes PerformancePerformance Pickup PatternsPickup Patterns Special UseSpecial Use

TypesTypes

All microphones are transducers.All microphones are transducers. Convert one type of energy to another – acoustic to Convert one type of energy to another – acoustic to

electric (speakers other way).electric (speakers other way). DynamicDynamic

Magnetic induction. Doesn’t need power, less Magnetic induction. Doesn’t need power, less expensive.expensive.

Moving coil – most common and durable.Moving coil – most common and durable. Ribbon – less common, more fragile.Ribbon – less common, more fragile.

Condenser (capacitor)Condenser (capacitor) Variable capacitance. Needs power.Variable capacitance. Needs power. Diaphragm and charged fixed plate.Diaphragm and charged fixed plate.

PerformancePerformance

Each microphone is different.Each microphone is different. Different frequency response.Different frequency response. Less mass of element, more responsive.Less mass of element, more responsive.

• Condensers often have less mass.Condensers often have less mass.• Less responsive does not mean better.Less responsive does not mean better.• As with all audio – it depends on what you are As with all audio – it depends on what you are

recording and what effect you want.recording and what effect you want.

Wind screens and pop filters.Wind screens and pop filters. Reduce pop from syllibants.Reduce pop from syllibants. Reduce wind sound.Reduce wind sound.

Pickup PatternsPickup Patterns

OmnidirectionalOmnidirectional Picks up sound more consistently from all directions.Picks up sound more consistently from all directions.

Cardioid (unidirectional)Cardioid (unidirectional) Picks up sound mostly from the front.Picks up sound mostly from the front. Heart-shaped (cardiac) pattern.Heart-shaped (cardiac) pattern. Proximity effect.Proximity effect.

• Picks up more bass close-up.Picks up more bass close-up.• Bass roll-off switch to compensate.Bass roll-off switch to compensate.

Super, Hyper: more directed pattern.Super, Hyper: more directed pattern. BidirectionalBidirectional

Picks up from sides best.Picks up from sides best.

Special UseSpecial Use System MicSystem Mic

Interchangeable heads for different pick up patterns.Interchangeable heads for different pick up patterns. Stereophonic.Stereophonic.

Two elements – right and left.Two elements – right and left. Binaural – recreates human head, but must be listened to on Binaural – recreates human head, but must be listened to on

headphones, so not commercially viable.headphones, so not commercially viable. Surround sound.Surround sound.

5.1 sound recorded on one multi-element mic or several 5.1 sound recorded on one multi-element mic or several separate mics.separate mics.

Other:Other: Lavalier – miniature for video or film.Lavalier – miniature for video or film. Shotgun – attenuates all but front, compresses distances.Shotgun – attenuates all but front, compresses distances. Parabolic – captures over long distances, lots of noise.Parabolic – captures over long distances, lots of noise. Adaptive Array – cancels unwanted sound digitally.Adaptive Array – cancels unwanted sound digitally.

Digital Audio Recording ProcessDigital Audio Recording Process

SampleSample QuantizeQuantize CodeCode

Step 1: SampleStep 1: Sample Snapshot of wave’s amplitude.Snapshot of wave’s amplitude. Samples “plot” the waveform.Samples “plot” the waveform. Two samples required to form a cycle.Two samples required to form a cycle.

CD-quality samples at 44.1KHz, since upper CD-quality samples at 44.1KHz, since upper limit of human hearing is 20KHz.limit of human hearing is 20KHz.

Low rate cuts high frequencies.Low rate cuts high frequencies.

Step 2: QuantizeStep 2: Quantize Sample snapshots may be at infinite points.Sample snapshots may be at infinite points. Must limit the number of choices and round to Must limit the number of choices and round to

closest.closest. 1-bit is either “on” or “off”.1-bit is either “on” or “off”. Each additional bit doubles possibilities.Each additional bit doubles possibilities. CD-quality is 16-bit, which allows for CD-quality is 16-bit, which allows for 65,53665,536

possibilities.possibilities. Higher bit-depth - higher signal-to-noise ratio – Higher bit-depth - higher signal-to-noise ratio –

more signal, less noise.more signal, less noise.

Step 3: CodingStep 3: Coding Takes the quantized sample and assigns it Takes the quantized sample and assigns it

a binary code.a binary code. A CD-quality sample, being 16-bit, would A CD-quality sample, being 16-bit, would

have 16 zeros or ones per sample.have 16 zeros or ones per sample. For example: 0110001101011001For example: 0110001101011001

Digital Audio Quality vs. File Digital Audio Quality vs. File Size ConsiderationsSize Considerations

Stereo or MonoStereo or Mono Halves file size without reducing quality.Halves file size without reducing quality. Reduces presence, sound placing.Reduces presence, sound placing.

Lower Sample RateLower Sample Rate Cuts higher frequencies.Cuts higher frequencies.

Lower Bit-DepthLower Bit-Depth Decreases signal-to-noise ratio.Decreases signal-to-noise ratio. Noise especially obvious with quieter signal.Noise especially obvious with quieter signal.

Compression CODECs are another subject for Compression CODECs are another subject for another test.another test.