Acx Test Passes on Audacity, but still sounds hissy/computer fan noise

Hi folks, a couple of questions for you please:

I’m narrating an audiobook for a client for ACX.
It passes the ACX test yet I can still hear the computer fan/hiss or both.
Don’t know if I’m being pedantic - I’m listening through headphones at about 50% volume.


Question 1: So if the ACX passes on Audacity it’s definitely suitable to pass when uploading to ACX?

Question 2: Will the Noise reduction (6,6,6) be enough/advised to take that final bit of noise away? (I’ve not had/got chance to test yet)

Tried the NS1 Noise suppressor in Reaper and it works great, yet fails the ACX pass.
Might be me being overly critical about the extra noise?

I’ve included a short WAV sample.



No the hiss is excessive. The settings you’ve used on the compressor has raised the noise-floor.

If you raise the noise-floor setting on the compressor (say by 6dB) on the unprocessed audio,
the level of hiss between words will be lower.


I’ve just recorded a Raw unaffected file attached - This passes the Acx test (Can’t hear any Hiss/Pc noise)

I then added the audacity effects to the recommended settings - Filter Curve, Loudness Normalization and Limiter, and I can hear the hiss/Pc noise now. (This also passes the Acx test)

Can you help please?

I’ve attached the Unaffected file.


The raw file is before you did anything to it, right? You have an odd collection of problems, but I think the first and most serious one is you’re not loud enough.

Your voice looks like this on the timeline.

Screen Shot 2020-12-06 at 2.53.02 PM.png
It’s supposed to look more like this (approximately).

Screen Shot 2020-12-06 at 2.53.33 PM.png
Your voice is an easy four times quieter than it needs to be.

Describe your microphone and the room. There are some tricks to get microphones to behave.

Some USB interfaces have volume indicators and they can get you in the ballpark quickly. One microphone interface has volume knobs that turn colors. It’s green when it’s happy.

There is one popular microphone that only recently told you in the instructions where the front was. It’s directional, so if you don’t hit it, your voice volume is reduced and can sound odd.

Pc noise now.

Those are not good English words. Can you tell the computer is on in the room just by listening? That’s not good news. The ACX specification for background noise is -60dB. In plain words, the background has to be 1000 times quieter than your voice. That’s not easy. If you can sit there quietly with a cup of coffee and identify sounds (refrigerator, traffic), that may not be a good room for recording.

Do you use any soundproofing? We publish plans for a “kitchen table sound studio.”



Yes that’s the Raw file.

I’m using a Rode Nt1a microphone with Pop shield into a Behringer Xenyx 802 via a Line in connection.

I have a Hobo Fort (Pvc pipe wardrobe) with 2 layers of moving blankets (each individual blanket is 2.6 kg) on all sides (floor and ceiling too)

I also have underlay carpet nailed to every wall.
This is all inside a cupboard (Just fits in)

Would it be better to increase the Gain level or General EQ level on the Behringer? Any rough guides for level setting on the Mixer?

The computer is in the adjacent room. Yes I can very faintly hear the fans whilst in my booth.

Any help appreciated.



Behringer Xenyx 802 via a Line in connection.

That may be one problem. The 802 is a perfectly respectable sound mixer, but most computers don’t have Line-In. Describe the computer. One of the problems I heard can be caused by this connection.

There is a Home Recording Conundrum. It’s usually best to keep the computer and its noisy fans far away from the microphone. You can adjust your voice volume by watching the Audacity screen. …*… Wait, you can’t easily do both.

Can you see the 802 controls while you’re announcing?


The 802 has a power supply brick, right? Plugs into the wall? Where is it? You should keep it away from the microphone or the microphone cables. The power supply brick for my tiny sound mixer hates microphones. MMMMMMMMMMMMM. That’s one of the lesser problems in your test sound file.


Yeah it has a power supply brick. It’s a couple of meters away from the mic. The PC has a dedicated line in.

I think I might have sorted it just by simply turning up the gain and level - like you said it was too quiet. I thought the added volume would pick up the fans more, but it seems okay now.

Can you test this attached raw file please?


Gotta love those heifers.

Did you notice all your noise problems vanished and simple, three-step mastering produces a marketable product?

Screen Shot 2020-12-06 at 16.43.49.png
I did this…

Which is lifted from this wiki posting.

You are warned, sternly, to take the steps in order, don’t add any, and don’t leave any out. It’s a suite, a harmonious grouping and they clean up after each other.

I’m not at my office machine, but as near as I can tell, it’s good to go. I do want to check one other thing. These microphones as a series are prone to “essing” where all your SS sounds are boosted. It makes my ears bleed, and I don’t like that very much, but it’s not that hard to adjust.

As we go.


Thanks very much.

Yeah I have the suite.
Can’t believe it was just volume - relieved though!

Yeah it’s a pretty ‘Essy’ mic but it’s all I can afford at the moment. I’m not great with D’esser progs.

Thanks muchly


Back in the office. I produced two mastered versions. One plain and one with DeSibilator applied to suppress Essing.

The crisp boosting is not that bad with this microphone and you may decide to just leave it all in there. I like the smoother DeSibilated version.

There is a “DeEsser” available, but I always had troubles getting it to work. DeSibilator is an improvement based on the original legacy code and it can produce very smooth, pleasant speech. These are the settings I used for you.

Screen Shot 2020-12-06 at 5.07.32 PM.png
desibilator.ny (56 KB)


The DeSibilator goes last! It uses the sound processing of the three tools in the Mastering Suite.

I don’t think I said that anywhere.


Thanks a lot. Appreciate that.