Audio Quality for Phone Calls

I’m delighted that the copper cable phone network is being shut off! Hooray!

Why? Because it used an old audio standard that carried about half of human speech frequencies.

This is the Speech Banana. It shows you how loud (dB) /what pitch (Hz) English speech is. A hearing test covers all these frequencies (pitches). So a spoken “S” is about 4,500 Hz, and 38dB. It’s really high pitched, and very quiet compared to an open mouthed “Aaaaaa” sound.

Old audio standards for copper wire cover 300Hz to 3,400Hz, so callers only hear a fuzzy mess instead of a distinct F, S, Th sound. Unless you are chatting to a bass/baritone guy, the clarity of speech is not good. And even with the bass there’s an issue, as nasal phonemes such as N, M get blurry too.

Mobile phones tend to default to “HD Voice” standard, which is 50Hz to 7000Hz. This is pretty good quality and normal-hearing users will be fine.

Some newer systems, such as 4G/5G mobile, use “Super Wideband”, which covers the whole range of speech/hearing, 50Hz to 20,000Hz. Each phoneme is distinct, as long as your caller doesn’t mumble, of course!

Without the copper wire network, we can expect phone calls to get much clearer, because the call is only as good as the lowest participant. A mobile can be great sound quality, but if it’s calling an old copper landline, the quality is bottlenecked by the inferior standard audio.

And this is why the phone has traditionally been a bugbear for hearing impaired people. Not only do you not have visual clues and lip reading, but your hearing aids can only amplify what they hear.

Technology is improving all the time. For hard of hearing landline users, the copper switch-off may force you to get fibre broadband and a new phone, but it’s going to improve your calls. The person at the other end will also be able to enjoy higher quality thanks to your upgrade.

And on that note, if you’re not already connecting your hearing aids directly to your mobile, ask your audiologist to tell you if your aids are compatible. This final piece of the chain means true High Definition calls all the way from the speaker’s mouth to your ear. You’ll be glad you learned how to use it!

Sally Jackson BSc (Audiology) RHAD MSHAA

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