audiobook harshness after using filters

I have followed the advice on how to adjust a recording so it passes the ACX check.

I first remove the slight background hum using Noise reduction.

Then I apply the three recommended Effects:

Effect > Filter Curve > Manage > Factoy Presets > Low rolloff for speech > OK.
Effect > RMS Normalize: Target RMS Level -20dB > OK.
Effect > Limiter: Soft Limit, 0, 0, -3.5dB, 10, No > OK.

After removing background noise again the clip passes the ACX check.

However the results are always a lot harsher than the original and lack warmth.

Attached are a clip before and after processing.

Any suggestions?


Now burn a new test using this formula. You can use the same words you used in the first two tests, but that quiet room tone two seconds at the beginning is very important. Do Not process anything. Read down the blue links. They’re very short.

What’s the microphone, how do you have it connected, and to what?


Thanks for the reply.

I’ve attached a 10 second clip following your instructions.

I’ve discovered the source of the hum - it’s the power supply in my Dell Inspiron laptop.

The previous clips had it on mains pwoer. Sample 3 is running on battery!

I’m using a USB Logitech headset with a boom arm microphone positioned just beelow my chin.



A 50Hz notch filter is a better tool for that, as it will do less collateral-damage to the speech than NR.

The nature of human-hearing is that the perceived frequency-content changes depending on volume …

Your “after” is considerably louder than the “before”, (~10dB louder).
So you’ll have to adjust the equalization to make loud version sound the same as the quiet version
(You may also have to use a de-esser).

There are free equalizer plugins which work in Audacity in Windows,
which behave like a real hardware equalizer that you can adjust in real-time when the audio is playing …

TDR Nova | Tokyo Dawn Records *
GVST - GMulti *

( * can equalize & de-ess at the same time).

I got the last one to pass ACX Check …

… but that’s only the first test for audiobooks. From there it goes on to Human Quality Control and I think you won’t make it past that. You sound like an air traffic controller for the same reasons they sound like air traffic controllers. Close-talking microphones with dense SS and SHSH sounds.

I applied Audiobook Mastering.

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Then Effect > Bass and Treble > OK.

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Effect > Hum Remover > OK

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And then finally Effect > De-Esser > OK.

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And you sound like a much more pleasant air traffic controller. ACX’s goal is for you to sound like you’re telling a fascinating story in real life to someone over cups of hot tea. No distractions.

I would be tempted to add the smallest noise reduction, but the clip passes as it is and you’re already up to, how many, six corrections and effects. Every time you open your mouth you’re going to have to crawl through all of those.

You can try a test submission that way if you want, but I think that would be wasted time.

I would tell you all about test submissions, but ACX changed it since the last time I looked. They’re harder now. Everybody with a pulse was submitting and they were getting overwhelmed.

They may pass it that way and you’re done except for all the work.


Not all of those tools are built-into Audacity. You’ll have to install RMSNormalize, HumRemover, and DeEsser.

Close-talking microphones with dense SS and SHSH sounds.

It is possible you sound that way normally when you’re ordering a cuppa from Tesco. Not everybody’s vocal oddities are an automatic rejection. I like a reader that has anything but a broadcasting voice and regional accents can be terrific in moderation.


Sorry. Missed one.


Thank you for all your help.

I have grabbed the additional plug-ins.

Maybe I sound like an airport announcer anyway :smiley:

I don’t mind having multiple effects to apply as I can create a macro to run them.


One caution about that. Effect > Filter Curve doesn’t always call the right curve in a Macro. You’re usually fine if you never use Audacity for anything else that needs different curves.

Maybe I sound like an airport announcer anyway

That occurred to me about the third listen. Maybe I’m correcting something that ought not be corrected.


Your turn. Write about your experiences submitting tests and your interaction with ACX (assuming that’s your target).


Well, after your comments and viewing some video reviews of proper microphones I’ve decided to get one and start again.

Thanks for the advice


Even with a new hum-free mic I think you’ll have to master the art of de-essing …

[ Add “JB Smash Pro” to the list of free [Windows] plugins which can equalise & de-ess ].

I’ve decided to get one and start again.

Post the idea before you write a check. I can point to glowing reviews of terrible microphones. While you’re working, Google [the microphone] Complaints. Anybody can pay people to write glowing reviews. That and reviewers might not review a bad microphone rather than offend people or start a flame war. So you have to search for the straight skinny.

And just to throw dirt in the game. I can pass ACX technical conformance and reasonable voice quality with that and a quiet room.

That is a Zoom H1n Sound Recorder (not voice recorder). It’s a little rough to use, so I can’t unconditionally recommend it, but it was $120 USD, it produces perfect quality WAV sound files natively, and it has zero computer recording problems.

From memory, I needed a little more height for the actual shoot, so I used three rolls of toilet paper. The toilet paper that’s now going for $35 a roll.


I got a new microphone:

Attached is the same text using this.

Any comments?



It’s a lot better than your previous microphone.
No noise reduction is required to pass ACX, just bass-roll-off to remove infrasound, (which is inaudible but is included in noise-floor measurements).
However I would use a (free) expander like couture which will to push down the noise floor by ~9dB and dry-up some of your slight room-reverb …

I got it to pass ACX with just the mastering tools.

There’s a fuzzy rule of passing -60dB noise by at least 5dB and yours is -66dB.

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