That reminds me of my short time with ISDN and the amazing availability to receive calls on the second line without forcing me offline.
https://www.microsoft.com/en-us/microsoft-365/business-insig...
They really do sound alot better. It always reminds me of the first time I ever made a FaceTime call, in 2010, and the high quality audio was just as interesting as the video.
If course it has to be pre-planned, someone needs to have the hardware with them. So sometimes there's a spontaneous connection over normal mobile phone. That's something that everyone has with them at all times.
24-bit samples is ridiculous overkill. That's a huge dynamic range that's completely unnecessary.
At 192KHz you'd be able to capture 96KHz signals, far, FAR outside the range of human hearing. Human hearing peaks at 22KHz so you only need a sample rate of 44KHz to capture the total range of human hearing.
For human voice you don't really need better than 16-bit samples at 12KHz or so. That's for great quality voice.
The only reason audio mastering is done at huge sample sizes and sampling frequencies is to prevent aliasing during mixing and to preserve higher frequency harmonics. There's absolutely no need for such rates delivering to human beings.
Also higher fidelity audio sampling is available for phone calls. The issue is more political than technical. Cellular carriers don't like to negotiate higher quality calls between one another so inter-carrier calls tend to fall back on the lowest common denominator AMR-NB codec. Intra-carrier calls don't even reliably pick AMR-WB let alone EVS available with VoLTE.
humans can’t hear above 20khz. adult humans can’t hear above 16khz or so, we lose the top end before age 20. this means that the standard 48khz sampling rate covers the entire human hearing range and then some (0-24khz). any sampling rate over 48khz for sound intended for human hearing is a total waste.
Also, you might possibly be sensitive to resampling artifacts if your output device runs at 44.1kHz and your file is 48kHz or vice versa.
Audio testing is hard, and testing on yourself is tricky... But if you have a sample that you're convinced sounds better at high rates than lower rates, I would urge you to put it through a tool to resample it down to lower rates and see if/when you can tell the difference. If the rate isn't an even multiple, it's worth using a tool that can dither; dithered resampling artifacts are less abrasive than undithered... I had some voice recordings to play over the phone, and everything needed to be 8kHz u-law; the 48kHz original recordings sounded better than 44.1kHz original recordings because one is even multiple and the other isn't, but either way, the waveforms looked worse than it sounded.
This seems to be mixing up two things; proper interpolation and dithering.
If you have limited bit depth (in practice, 16 bits or worse), you should pretty much always dither, ideally also noise shape. This is independent of the interpolation you're using; having a rational relationship between the original and downsampled signal makes some of the implementation a bit easier, but even for something like 48000 -> 24000, you'll end up with effectively a float signal that you need to convert to your chosen bit depth somehow, and that should be done better than just truncating/rounding.
And even for interpolating between two prime rates, or even variable-rate interpolation, you can and should get great interpolation (typically by picking out polyphase filtering coefficients from a windowed sinc of some sort).
"Headroom"
And the idea that humans can't hear over 20khz is like "humans taste 'sweet' on the tip of the tongue, and 'bitter' on the sides"
As we get older the hairs in out ears break or whatever and our perception decreases, but I could hear the fly backs in my old monitors, I used to be able to see the flicker in 3khz pwm LEDs, and my induction hob drives my kids crazy but it's merely midly annoying to me.
Get a real soundcard and some young people and play square(pwm) and sine tones starting at 16khz and find out where they can't hear it anymore. I find studio monitors with tweeters that are not paper are the best.
The extra headroom can indeed be useful for some kinds of processing, but you can safely discard it for actual listening.
Are they the exact same volume? We perceive things slightly louder as higher quality.
Is it a double blind test, ie an ABX test?
Are the bit depths the same? Many 96khz sampled files use 24 bits per sample, whereas 48khz usually uses 16 bits per sample.
but you do need phile-enough gears(minus the gilded pebbles hot glued onto circuit breakers)
The big issue with analogue landline phone calls is the audio bandwidth is so limited. It's not the full frequency spectrum, most of it it cut off.
EDIT: I do agree that lossless (or at least high bitrate modern lossy, like 256k Opus which is basically transparent) should be available in many more situations though.
https://en.wikipedia.org/wiki/Comparison_of_audio_coding_for...
https://en.wikipedia.org/wiki/Opus_(audio_format)#Quality_co...
I was talking to a sales rep, at the time I worked for USWest or QWest, whatever they were called at that time, which may have helped, and the sales rep told me "we are being told to actively discourage people from buying ISDN".
I get the impression that the phone company hated consumer modem use of any kind, because it tied up CO equipment 24x7, and they liked the returns on investment they got with people paying $25/mo for resources that were used an hour or less a day, sometimes with extra revenue from long distance calling. And ISDN was just another representation of that.
We could do this since local loops to most folks were about $150-200/mo, and we already had a channelized DS3 terminated at our rack at a local datacenter for our phone banks. If you bought your own DS1 retail you'd be paying upwards of $1k/mo back then to a provider.
It was by far the best "stickiness for dollar" investment into employee benefits I've ever found back then or since.
And I accessed the heck out of that connection (until the ISP went bust, wonder why?), and was very much a Q3A LPB during that time.
Fast-forward to 2025, and I now have dual 1Gbps symmetric fiber connections (AT&T, GFiber) into my home from opposite sides of the house. (It's totally gratuitous and I'll probably cancel GFiber in a few months, but I wanted to have it wired up so I could more quickly start service in the future.)
https://en.wikipedia.org/wiki/Ricochet_(Internet_service)
Wireless 56k baud. So you could take your luggable laptop circa 1994 with you and dial in to work... given you lived in SF.
One of my internships in college was at Sun Microsystems in the org that provided this connectivity to employees. My job was to automate pushing updates to connection software and modem firmware down to clients, but I ended up doing a lot of technical support as well.
The other (often overlooked) benefit that ISDN provided was 24/7 connectivity in an age of dialup.
Oh and you could spoof your outgoing phone number for caller ID ]:D
If they had gotten out of their own way when the internet came around they could have charged a small monthly fee to upgrade to a "digital phone line". Lots of people would have switched.
My dad ran a BBS from like 1992 to 1995, which started falling out of favor, especially as the users were getting more busy signals because the modem phone line was tied up with the internet connection.