Sound is way off


Preface: total newbie.

Intent: Produce quality sounding audiobooks for ACX.

Issue: Meeting ACX required RMS and Peak Values destroys sound quality. Comes across as way too loud, robotic, and mechanical.

Settings: Max playback and recording volume. Max speaker and microphone volume. Gain, 0.

An audio recording without any added effects has a very low RMS and Peak value.

Peak level = -15.53 dB
RMS level = -37.33 dB
Noisefloor = -60.64 dB

Followed standard instructions to meet ACX criteria i.e.: effects low-roll-off speech EQ, RMS normalization to -20 dB, limiter to 3.5 soft limit, and noise reduction (based on the noise profile for the first 5 seconds of silence).

The revised audio file meets the ACX check, and the Audiolab verification tool on ACX, but the audio sounds terrible. It sounds like the volume is cranked way too high, with a mechanical tonality to it.

The ACX check doesn’t always work. In order to meet the Audiolab verification too, I’ve had to program audacity to the following settings:
-Peak level: cut off to -6.5 dB
-RMS normalization to -23
-Noisefloor to -25

Any advice would be much appreciated.


Check Windows “audio enhancements” are disabled
Disable recording & playback enhancements for faithful sound.

BTW there can also be a second layer of “audio enhancements”
such as MaxxAudio, or DTS, (depending on computer manufacturer).

That’s very low. Here are some possible explanations …
Speaking into the insensitive side of microphone.
Accidentally recording from computer’s built-in in microphone.
Not supplying phantom power to a mic which requires it.
Mic level slider in Audacity not turned up to maximum.
Mic has gain knob which is not turned up high enough.
The mic level slider(s) within Windows sound not turned up high enough …


Thanks so much for the reply. I really appreciate you breaking it down. I disabled the “audio enhancements” which improved the quality a bit. The RMS level is still way too low, i.e.: in the -30 range. I’ve gone through the settings, and none of the explanations you’ve highlighted apply. I’m using the MAONO AU-PM421 Mic, which is a budget microphone, however the manufacturer does not identify the requirement for phantom power.

Could it be anything else…?


It’s a USB mic, so does not require phantom power.
It has a gain knob on it, that should make things louder/quieter …

Mic Gain Knob: Flexible Gain Knob can increase the volume and sensitivity of the USB gaming microphone,

The mic gain knob must be facing the performer: that’s the sensitive side of the mic …


Ah. The sensitive side wasn’t quite facing me. Having adjusted my mic, the RMS is much better hovering around -20. Sorry for the rookie mistake, and thank you so much for taking the time to troubleshoot it with me.


Exactly correct. But there’s way to not work that hard. We publish Audiobook Mastering which is a one-step tool to automatically apply all three effects.

There is one soft correction. You should not be applying Noise Reduction customized for each chapter. ACX demands all your chapters match. If you do require Noise Reduction (some recording processes don’t) you might see if Noise Reduction of the Beast (6, 6, 6) will do it for you. That’s a nice, gentle reduction and nobody can tell what you did. The fuzzy rule is passing the -60dB noise limit by at least 5. So -65dB.

Unless they changed it, on-line ACX Audio Lab doesn’t check noise. Audacity ACX-Check does.

It’s good to know what your noise is. If it’s gentle, Spring Rain in the Trees (shshshshsh) then that’s normal, although a USB microphone should not fail that right out of the gate.

There are other noises, some of them pure evil. There is a USB error caused by both a cheap, inexpensive computer that doesn’t cost very much and a similar microphone. It causes digital trash to leak between the wires of the USB cable. It sounds like screaming mosquitoes and more importantly, will cause your voice submission to fail Human Testing even though the file passes ACX-Check.


If you’re having distortion problems you may have some odd errors. Post a sound sample so we an hear it. Nothing like trying to guess at a mystery problem across multiple time zones. Sound samples help.

Don’t help it. Just post what you got.