![\"MP3](\"https:\/\/cs.stanford.edu\/people\/eroberts\/courses\/soco\/projects\/data-compression\/lossy\/mp3\/fig20_psychoacoustic.gif\")
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Introduction to sound<\/p>\n
![\"Psychoacoustic\"](\"https:\/\/www.mdpi.com\/applsci\/applsci-09-02854\/article_deploy\/html\/images\/applsci-09-02854-g004.png\")
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Definition: Sound is a sound wave produced by vibration, a wave phenomenon that propagates through a medium (gas, solid, liquid) and can be perceived by the hearing organs of humans or animals.<\/p>\n
Essential: Sound is a mechanical wave.<\/p>\n
Three elements of sound.
\nTone : sound frequency (audio), boys > girls > boys
\nVolume: The amplitude (amplitude) of the vibration, also known as the pitch
\nTimbre: The waveform of the sound, which is essentially harmonic, also known as fret, has a lot to do with the material
\nIcon:<\/p>\n
tone and volume<\/p>\n
doorbell<\/p>\n
psychoacoustics
\nPsychoacoustics is the study of human perception of sound, that is, the science of human physiological and psychological responses to sound (including speech and music).<\/p>\n
hearing\/voice range
\nhearing range<\/p>\n
sonar heading and range<\/p>\n
audio quantization
\nquantification process
\naudio quantization<\/p>\n
basic concept
\nSample Size \u2013 How many bits are used to store a sample. 16 bit common
\nSampling rate : 8k, 16k, 32k, 44.1k, 48k sampling rate
\nNumber of channels: mono, dual, multichannel
\nBit rate calculation
\nBit rate = sample rate \u00d7 sample size \u00d7 number of channels<\/p>\n
What:<\/p>\n
The sample rate is 44.1 kHz, the sample size is 16 bits, and the two channel PCM encoded WAV file<\/p>\n
Bitrate = 44.1k \u00d7 16 \u00d7 2 = 1411.2kb\/s = 176.4KB\/s<\/p>\n
audio compression
\nAudio compression is a type of data compression used to reduce the transmission bandwidth requirements of streaming audio media and the storage size of audio files.<\/p>\n
compression method
\nlossless compression
\nAll the information of the original file is preserved and there is no difference from the original file on playback.<\/p>\n
Data compression through information redundancy is a reversible process.<\/p>\n
lossy compression
\nApproximate some information in the original file to get a smaller file.<\/p>\n
The incorporation of human psychology and recognition of the auditory system in the compression results is an irreversible process.<\/p>\n
Audio signals outside the range of human hearing and audio signals that are masked.<\/p>\n
masking effect
\nMasking effect: A phenomenon in which the auditory system’s perception of one sound is obstructed by another.<\/p>\n
frequency domain masking
\nOne sound is drowned out by another sound at the same time.<\/p>\n","protected":false},"excerpt":{"rendered":"