Need help with my sound in order to pass Audible ACX Raw sample file - I’ve just chopped out any speaking mistakes but haven’t applied any filters or effects.

Hello, my name is Barbara and I have been doing voiceover work from home for some time now, slowly increasing my entirely self-taught knowledge and upgrading both equipment and my room as profit permits. I recently have been hired to record 2 audiobooks, and I have never dealt with ACX regulations before, and admittedly know very little about all the technical audio terminology and how to achieve effects the right way with Audacity. I have basically picked up a few tips and tricks here or there and just made them work well enough for the jobs I’ve had thus far. But I really would love some help from the experts on how to improve my raw sound and then what effects to apply, in what order, to achieve my best results.

I am using Audacity 2.1.1 completely out the box, don’t know anything about downloading any custom filters or anything of that nature.

I record with a Rode NT-1 mic, attached to a desk boom stand with the included shock mount and pop filter that came with it.
It runs through a (brand new, still figuring this out) Wharfedale Pro Connect 120FX/USB mixer, then into my iMac Retina 5K, running El Capitan 10.11.5
I am recording straight into Audacity.

My mixer is a brand new purchase, my husband bought it for me so that we could try to improve the level of my input from my mic, which used to run through a PreSonus AudioBox iTwo, but even when the gain was practically maxed, I could barely get a visible waveform because the input was so weak. With the new mixer, I have a really hot input, which barely needs any normalization, but the board seems to have this really loud hum that doesn’t vary at all no matter what I do (trust me, I’ve recorded with the gain all the way up/turned it all the way down/unplugged the mic completely/turned off the phantom power - all of these result in the exact same hum being picked up by Audacity with absolutely audible no variation.) So now I just want to figure out how to filter it out, reduce it, and improve my overall sound with the help of the kind contributors here.

Normally, I just do Compression, Equalization Bass Boost, Equalization Treble Boost, Normalize, Hard Limiter. Then I do a Noise Reduction (sometimes it takes two rounds of Noise reduction to get all the noise out, but gets that slight underwater sound). Like I said, I don’t know what I’m doing LOL

Are you using our ACX-Check tool? This has come up enough times that FlynWill developed a tool to make all the cardinal ACX measurements in one swoop.

And I wrote the short page on what those numbers mean.

You found a violation of my assurance that any mixer with 48 volt Phantom Power should not have sound problems. You have “The Dreaded Yeti Curse…” When you stop talking, you have that high-pitched mosquito whine in the background. That’s not a simple noise reduction problem. That’s rough to get rid of.

I need to read over your information again.


ACX-Check tool

Apparently, nobody wrote the user guide.

After you install the tool software. ACX Check shows up under Analyze.

Screen Shot 2016-06-03 at 3.16.55.png
Note you also have to pass Human Quality Control. This is where your overly noise-reduced, honky voice is going to die, and Yeti Curse will cause failures, even if the clip actually passes ACX Test. No, it’s not that unusual. This is trying to ignore a baby screaming on a jet…

The Blue Yeti (not the Pro model) is an insanely popular single-sitting USB microphone. One of the reasons it’s popular is the price. It’s cheap. Because of that, it has little or no filtering to keep the USB data sound (high-pitched whine) out of the show sound. Most Of The Time you don’t have to worry about it, but if your computer and the Yeti hate each other…zzszszsssssszzzzszszszszszzz.

Typically, if you went to the bother to create 48v Phantom Power (which your mixer does), you already have the processing and filtering available internally to get rid of Yeti Curse. That would be good engineering practices.

Can you change the mixer USB cable? It’s a printer cable, right? A to B. This isn’t a good place to put a USB cable extension or USB hubs. Those can cause problems. Is the whine different if you use different microphone connections?


Hi Koz,

Thanks for the reply, we have switched out the USB cable with two others and there was no change. Also, not sure why you you keep referencing the Blue Yeti USB mic, as that is definitely not what I have :stuck_out_tongue: Mine is an XLR - the Rode NT-1 (not the NT-1A either which is also popular)

After digging around I did just download the ACX-Check tool and see that it is passing “technical” requirements but obviously I need to get rid of this noise before I can submit it. Any suggestions on the best way to post-process this out would be greatly appreciated (and please be specific with settings and order of steps from start to finish because as I said I’m only going be generic YouTube help videos, that have nothing to do with my specific needs but seem to be making a marginal difference. I absolutely know that I can do much better if I understand the process and tools better.

Thank you :slight_smile:

Oh forgot to also mention that we have 2 XLR cables, and changing between them also made no effect to the sound.

Looks like a ground loop to me…

Constant hum doesn’t look like the Yeti curse.

Also, the NT1 has got a strong output signal. If your Presonus Audiobox couldn’t amplify this mic to a decent level, it’s broken.

Possible cause of the hum: defective mixer preamp or most likely, a problem with the mains connection grounding.

If you are recording with a laptop, try it on battery. If it’s a desktop, check if your mains connections are all properly grounded.

EDIT #26: If the hum is present even with nothing attached to the mixer, there’s a high chance you have a defective mixer. If you can exchange it, I would advise an interface in stead of a mixer because you don’t need a mixer (and the effects in that mixer probably degrade the sound a bit) and in general the quality of audio interfaces is better. Take a look at the Focusrite 2i2, Steniberg UR22 or even the new Behringers.

not sure why you you keep referencing the Blue Yeti USB mic, as that is definitely not what I have

Because that particular noise is so common, it has its own name. It’s not “hum.”

As you’re finding, you can pass ACX Check and still have that whine sound back there. I applied a custom filter that someone wrote to suppress it, but the suppression didn’t work. Jury’s out why.

It’s very valuable to get rid of it before you start reading. This is not something you can get rid of easily in post production by pushing a button or applying a filter or effect.

Or you can, but I think you noticed already, it’s possible to produce a technically perfect work that doesn’t sound like you.

I have a Behringer UM2. There is a newer one, the UMC22 with better sounding electronics.

I was able to create a clip that passes ACX with my little UM2 and a rock band microphone in a quiet room. Finish recording, change the volume a little to conform with ACX and go home. If you’re struggling to create a normal voice track with much better equipment, that’s a problem.

And yes, I, too, think there’s something wrong with the Presonus, your original USB device. There’s nothing bashful about a Rode NT-1. It’s one of the microphones listed in the ACX recommendations.

Where did you get your XLR microphone cables from? They are straight Male to Female, right?


The posted recording is very quiet, and i hear no trace of mains hum. There is a tiny bit of 1kHz USB whine, but it is well buried in the white noise of the mic preamp. If you are hearing hum in your setup it is in whatever is driving your headset and/or speakers.

Thanks for pointing that out, Flynwill. I completely missed the sample recording and was going by what I read only.

There’s a whine there. And some clicks that sound like USB transport clicks. Or is it background noise from the room? It’s not too bad, though. I’d still try another audio interface as I fear that mixer isn’t very well protected from USB noise coming from the computer. And the NT1 is one of the quitest mics on the market. It seems like a shame pairing it with a somewhat noisy mixer.

Sorry, Koz! You were right again.

Rescue time!

Someone posted Nyquist code to get rid of that whine. I tried one and it was awful. Pretend I didn’t find it. What’s the code for that?

I think I see spikes at 1 Khz and 2 KHz. I think Flynwill said those are the USB supervisory negotiation channels?

I think no matter who listens to that clip is going to pick that out, further, I think that’s what’s causing the poster’s multi-pass noise reduction to create sound damage.