ACX distorted/lowered quality after publishing

Hi guys,
I just published my first audiobook through ACX, and I heard ACX can sometimes lower the quality once it’s published, but the background noise is higher and my voice sounds more muffled.

I compared my mp3 files and even went into my “produce audiobook” section on ACX and played back the finished, uploaded files and compared them with the published files on audible and it’s a huge difference! My book sounds much clearer and crisper before publishing. What’s up with that?
If it sounds good on my end, how am I supposed to prevent this same issue in the future? So frustrating!

For reference, you can listen to the sample here:

My finished files don’t sound like that… any help appreciated!

I’m not able to listen to that as I don’t have an account, but possibly the on-line previews are lower bit-rate than a purchased download.

Thanks for the quick reply.

You can also listen here without an account, I believe:

I was hoping it was just the sample, like you mentioned, but I purchased the book and gave it a listen and it’s also muffled/lower quality than the actual files.

Not sure how to solve this kind of issue, it’s clearly something ACX does on their end before upload, but I don’t want authors to think I’m not capable of delivery good quality…

Yes the preview is relatively low quality (high compression).
I can’t tell exactly what they have done, or what the exact “kbps” is, but it is probably fairly low kbps. We can see that frequencies above 10 kHz are absent:

First Track000.png

Ah, I see. Right. Assuming I have the settings correct on my spectrogram preview, the original file does go much higher.
Does anyone have any thoughts on what I can do to preserve this quality so ACX doesn’t lower it too much? I know plenty of other narrators manage to get top quality content out (though perhaps their studio’s are higher quality as well), so I’m sure there’s something I can do, I just don’t know what…
Thanks for the help.
Screen Shot 2021-03-18 at 1.46.30 PM.png

There’s not much that you can do. It’s mostly in the hands of ACX.

The only thing that you can do is to submit your work in mono, at the highest bit-rate that ACX allow (check their current format specifications). Beyond that it is entirely in their hands.