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COSC 414 Audio in Games Digital Audio -- Part 1 Sound Something vibrates in the air creating waves of pressure on your eardrums that your brain interprets as sound. Sound pressure measured in decibels , dB. 0 dB - Threshold of hearing 10 dB - Rustling leaves 20 dB - Whisper

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COSC 414 Audio in Games

Digital Audio -- Part 1


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Sound

Something vibrates in the air creating waves of pressure on your eardrums that your brain interprets as sound.

Sound pressure measured in decibels, dB.

0 dB - Threshold of hearing

10 dB - Rustling leaves

20 dB - Whisper

60 dB – Conversation

110 dB – Rock Concert

130 dB - Threshold of pain

160 dB – Instant perforation of eardrum


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Sonic Elements

Audio Types:

Music

Voice Over

Dialog

Sound Effects


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Audio Uses:

Alert

Information

Mood

Sonic Elements


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Digital vs. Analog

Wave Forms-

Analog = continuous

Digital = discrete

To convert from analog to digital: sample -

Look at amplitude at regular intervals

Convert to a number

Use number to play back the sound.


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Digital Audio

Sampling

1Hz=1 Hertz = 1 cycle per second

Sample rate

Telephone Quality 11 KHz, 8 bit, mono

Radio Quality 22 KHz, 8bit, mono

CD Quality 44 KHz, 16 bit, stereo

As sample rate increases ...

Quality increases

File size increases

Fundamental Problem of Multimedia:

Balance file size with asset quality


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1 byte: +/- 128 discrete values

2 bytes: +/- 32767 data points

1 minute of CD quality audio

44100 samples per second

X 2 bytes per sample

X 2 channels

X 60 seconds

10.5 Mb per minute

Sampling Rates

http://gwc.sourceforge.net/gwc_science/node2.html


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Compression

Holy Grail of Audio:

Develop the best algorithm, one that combines high quality at low bitrates and works everywhere.

First standard in audio compression: MPEG

This algorithm was developed by the Motion Picture Experts Group (MPEG), as an International Organization for Standardization (ISO) standard for the high fidelity compression of digital audio.


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Psychoacoustics

How does the human audio perception influence compression?

Human hearing masks weaker signals whenever the presence of a strong audio signal makes a temporal or spectral neighborhood of weaker audio signals imperceptible.

“Selective Hearing”

http://www.dtic.upf.edu/~xserra/cursos/TDP/referencies/Pan-Davis-IEEE-MJ-1995-MPEG-Audio-Compression.pdf


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Production Values

Sound Studio

Professional Voices

Ambiance, Decay, Echo

Plan using the Storyboard

Get it all in one studio session

Professional Audio Editor


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