Audio

Jun 28, 2018, updated Aug 11, 2019 General

see this Digital Audio: The Line Between Audiophiles and Audiofools

Audio

Frequency Range Of Human Hearing: 20HZ - 20,000HZ

Low Frequency Range Test (10-200 Hz) High Frequency Range Test (8-22 kHz)

Noise level

See this

Painful impulse noise—Not safe for any period of time 150 dBP = fireworks at 3 feet, firecracker, shotgun 140 dBP = firearms Painful steady noise—Not safe for any period of time 130 dBA = jackhammer 120 dBA = jet plane takeoff, siren, pneumatic drill Extremely loud—Dangerous to hearing; wear earplugs or earmuffs 112 dBA = maximum output of some MP3 players, rock concert, chainsaw 106 dBA = gas leaf blower, snow blower 100 dBA = tractor, listening with earphones 94 dBA = hair dryer, kitchen blender, food processor Very loud—Dangerous to hearing; wear earplugs or earmuffs 91 dBA = subway, passing motorcycle, gas mower Moderate—Safe listening for any time period 70 dBA = group conversation, vacuum cleaner, alarm clock 60 dBA = typical conversation, dishwasher, clothes dryer 50 dBA = moderate rainfall 40 dBA = quiet room Faint—Safe listening for any time period 30 dBA = whisper, quiet library

Compression

Non Compression audio or Linear PCM has Bit Rate of 1,411 kbps.

Example:

Lossless

This is good will keep the original quality of the audio.

Example:

Lossy

This is bad. It will loss some quality of the audio

both Lossless and Lossy

Some audio formats feature a combination of a lossy format and a lossless correction; this allows stripping the correction to easily obtain a lossy file.

Recommendations

settings

on Mac use this app Applications > Utilities > Audio MIDI Setup

Commands

brew install ffmpeg mpv youtube-dl

show information about the audio:

ffprobe file_name 2>&1
ffprobe file_name 2>&1 | sed -E -n 's/ .*bitrate: (.*)/\1/p'

Notes

lossless size

The ‘bitrate’ of the lossless compressed file, not the original material, will achieve different amounts of compression with different audio source material - some audio compresses easily and some does not, so it will vary.

Uncompressed audio from standard CD has a fixed bitrate. It is stereo (two channels), 16 bits per sample, 44,100 (44.1 kHz) samples per second.

2 x 16 x 44,100 = 1,411,200 bits per second (bps), or approximately 1411 kbps

But when compressed using FLAC or another lossless codec, the bitrate will be less.

30% compressed -> (1 - 0.30) x 1411 = 988 kbps 40% compressed -> 847 kbps 50% compressed -> 706 kbps 60% compressed -> 564 kbps 65% compressed -> 494 kbps 70% compressed -> 423 kbps

References