eli5: Why hasn’t the audio quality of “on hold” music improved in decades?
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I saw this earlier today and I think it’s related. [https://www.reddit.com/r/whatstheword/comments/13idmkx/wtw_for_a_kafkaesque_appeal_process_designed_to/](https://www.reddit.com/r/whatstheword/comments/13idmkx/wtw_for_a_kafkaesque_appeal_process_designed_to/) On-hold music is designed to be so unpleasant that you hang up and prevent the company from having to provide you with support.
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It’s because the actual total quality of phone calls themselves has actually decreased over the years. Phone companies have crushed bandwidth down to what barely allows for human speech to be understood. Music of any complexity can’t sound good in that situation. It would probably actually sound better if they used MIDI music.
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Since 1972 telephones have adhered to a standard that converts sound into digital signals 8000 samples every second or 8000 Hertz (Hz). A tone with a frequency of 200 Hz collects 40 samples each cycle; a tone of 2000 Hz collects only 4 samples within a cycle. The higher frequency that a sound has, the fewer samples per cycle are collected. With fewer samples per cycle it is harder to reproduce the sound accurately when played back at the other end.
All the effort of improving phone codecs has gone into making speech clearer over low-bitrate channels. This has resulted in speech codecs that are completely different from general-purpose audio codecs like you would use for music or the audio track of a movie – you are not trying to squeeze a diverse type of sound into 100 kbit/s, you are trying to squeeze a very specific kind of sound into something likt 2 kbit/s. As a result, those codecs are hyper-optimized for stuff like human voices – any bits spend to encode non-voice sounds would hurt efficiency. And music typically includes instruments that sound nothing like a human voice, which results in them getting mangled to hell.
Back in the days of analog audio (and primitive digital audio for that matter), there was little in speech-specific processing, so while early digital phone systems had mediocre rendering for speech and hold music alike, the digitization process also did not actively mangle the music – in effect, hold music has even gotten worse because we have gotten more effective at stripping speech to its bare essentials. Plus phone services are always eager to fit more customers into the same bandwidth, so a lot of the improvements in speech compression were actually eaten up by that instead of going into clearer speech as well
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