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[Dallis24F]

If your app removes chapter marks when converting from 64 to 32Kbps and you want to keep them, use inAudible to convert it.

[franniebr]

Is 32 kbps the preferred bit rate? I've been wondering... I've been doing 96 or 64...

[Dallis24F]

I think most people like 64 but, I use 32. It sounds about the same to me and uses less battery power. 

22.5 kHz is normal for both 64 and 32k.

Books and broadcast like GraphicAudio are normally posted at 256k but I convert mine to 128.

[Lieve]

While Dallis does indeed love 32kbps, there is normally quite a big difference in quality. Oftentimes the 32kbps is ... just not good enough. 64kbps is perfect in my opinion.

[Gweilo]

64kbps is perfect

It seems you both use and CBR. Why?
A VBR with an average of about 32 gives you the equivalent of 48 or 64 CBR, at half the size.
You can look at the instantaneous bitrate  in e.g. MP3DirectCut to see how it works. Silent sections go down to 8 kbps; complex ones go up to 48, 64 or higher as necessary to retain quality.
The 320kbps CBR audiophiles can encode silence and waste gigabytes.

The only advantage of CBR is that it's easier to understand.

Example (an extreme case, admittedly):

The book "Replica" was uploaded as a 320 kbps CBR rip,
https://audiobookbay.lu/audio-books/replica-lauren-oliver/
   2.12 GBs


I thought this was a bit absurd, I made a rip using VBR quality 9:
https://audiobookbay.lu/audio-books/replica-lauren-oliver-2/
   153.78 MBs


1\14th the size, and if you can hear a difference in quality, I congratulate you on your golden ears.

Apple's AAC, used in iTunes and Audible M4A and M4B, uses VBR, the bitrate recorded for those is the average, not CBR.
https://en.wikipedia.org/wiki/Audible_(store)#Quality
But those making MP3 still use settings from the 1990s when VBR was weird and untrusted.

[Horstman]

* sets mode +golden_ears Horstman :P

VBR -9 seems a bit extreme low to me.
I usually start hearing the difference from quality -3 and down if one has a clean source. For my personal library I therefore opt for -1 or -2. Yes, the filesize may increase abourt 1/4th from an Inaudible 64Kbps AAC MP4, but I want my results to be transparent.

For generally satisfying results, I usually suggest VBR quality -3 to -5; especially with direct Audio CD rips.

Yet this all depends on how golden your ears are... I think the best suggestion for other users is to try out a couple of different VBR quality settings. (For example -2, -4 and -7).
And I totally agree that everyone should opt for variable bitrate encoding whenever possible.

[Gweilo]

Yet this all depends on how golden your ears are... I think the best suggestion for other users is to try out a couple of different VBR quality settings. (For example -2, -4 and -7).
And I totally agree that everyone should opt for variable bitrate encoding whenever possible.

Yes, I  won't dictate which quality setting works for everyone.
I have very cheap earbuds and listen while I'm walking, so hifi is lost to me.

My main point is, FFS, do choose a quality setting, use VBR, You can get 64k CBR quality in 32k VBR size.
The ratio is similar for higher quality if you have a betters source and are a more demanding listener.

[Horstman]

Absolutely. Even with the highest possible variable bitrate setting - which is "more than transparent" - you'd never end up with files as large as 224 or insane 320Kbps CBR. It would rarely go above 180 - and that is with complex music right from a pristine source, not the usual audiobook...