Two different sessions, two different ACX issues

I am recording using a Blue Snowball plugged into an iPhone 7 running the Voice Recorder Pro app.

(It’s the most portable solution I could get, just using an isolation shield in an otherwise untreated room. I expect I need to have more than the shield.)

I really would appreciate some expert ears on a couple of samples. One was recorded maybe a foot away from the pop filter; the other was closer to the fist distance. ACX Check says both are bad, for different reasons. Apparently the noise floor on my room tone is bad as well.

In both these cases, is more thorough soundproofing the solution?

For these specific clips, how should I improve them? These specific clips aren’t for ACX.

Any help or clarifying questions would be greatly appreciated. I can hear someone mention “buffet” from 10 meters away, but I cannot pick out all the fiddly issues in a clip of audio.

The mic and/or hardware used to record those is different:
e.g. the second example (388.04 KiB) has USB microphone whine artifact noise, the first one doesn’t.

At some point you may be speaking onto the wrong microphone,
e.g. the second example (388.04 KiB) could be you speaking into the external mic,
but actually recording from the phone’s inbuilt mic , (giving a quiet, muffled result).

If you (gently) tap the phone then the external mic,
you will be able to tell which one you are recording from.

If you (gently) tap the phone then the external mic,
you will be able to tell which one you are recording from.

Or scratch.


Thank you for the advice!

Next step: to get rid of USB microphone whine artifact noise?

Most people can’t read directly into ACX submission. You have to apply some corrections. We have a mastering suite of tools which will take care of that.

But I don’t think wild reading is what’s wrong with the noise floor measurements. In order to inspect background noise, there has to be some background noise. There isn’t in either of your two clips.

Please read 20 seconds according to this formula.

I didn’t just make that up. This is a shortened version of the test clip submission requirement for ACX.

I agree, those seem to be two entirely different microphone systems and to my ears, the most objectionable sound quality is RMS Fail…. That one sounds like bad cellphone or noise reduction or compression processing damage.

Pick one of the two systems and let’s see if we can nail down those problems and then switch to the other.


There is an Audacity plugin for that : Mosquito Killer.

We should note that Mosquito Killer removes the “frying mosquito” noises by deleting the whine noise and many of the overtones and harmonics from he show…and your voice. It’s not free.

You get Frying Mosquitoes when you connect a sloppy microphone to a sloppy computer—and it’s not 100% effective as there are some similar distortions that Mosquito Killer can’t manage.

Your mileage may vary, etc.

Correct me, but the bottom of an iPhone7 has a lightning port, not USB. So you used an adapter to connect the Snowball? I guess it’s possible the new Snowballs have a different connector, too. Mine had a USB-B socket for a “printer” cable.

It’s still valuable to get that test clip as I couldn’t hear the mosquito noise in the very short spaces between words. That two second gap is valuable even if you’re not posting to ACX. The ACX specifications are scary close to Broadcast Proof Of Performance, so if you can pass one, it’s very likely you can pass the other. In general, if you can pass ACX, you can successfully post to any other service or product.

To cut to the chase, Bad Noise Floor has excessive volume and peak distortion and RMS_Fail has digital compression and auto noise reduction distortion. There isn’t enough clean background noise to measure accurately.

Mosquito Killer won’t help any of those problems.

Open Bad Noise Floor in Audacity and View > Show Clipping. That blast of red on the timeline at about quarter second is too loud and distorted.

Screen Shot 2019-04-26 at 20.39.19.png

Thank you x2, Koz. I appreciate your taking the time. (And thank you Trebor for the Mosquito Killer recommendation.)

You are correct, Koz: I was using a USB-B to Lightning adapter cable to connect the iPhone 7 and the Blue Snowball.

I read the following per your specifications (and I honestly did pronounce “KozCo” correctly, at least in my brain), trimmed the WAV in RX6 Elements, opened in Audacity, and exported as a WAV.

You have at least two different noise problems, you lucky dog.

As above, you have Frying Mosquitoes and a very high plain microphone hiss. After accounting for those, you pass ACX Check by the thickness of a piece of typing paper. Remember typing? On paper?

I need to get back to the office machine to see if there are any other problems in addition to that.

You may need to change your announcing style (although the theatrical style is fine).

Why are you in love with a portable system? If that’s important to you, I would so use an actual sound recorder and avoid all those conversions and adapters. That and the Snowball is not the best microphone in the world and it’s large and awkward.

Screen Shot 2018-12-21 at 14.23.13.png

That’s an older Zoom H4. Another poster seems to be happy with a smaller H2n recorder.

While you are correct my “Z” would be pronounced “ZH” in the old country, nobody in my family has pronounced it that way in decades.


(My brain was telling me to make an ordinary Z sound, but it came out like “Kosh.” I think it’s a dental issue.)

I am pleased to hear that there is hope for making ACX. (I generally use 20-pound bond, though I’ve no longer my pristine '50s portable. I tried typing out some fiction and running that through a Roadwarrior portable scanner, but it was too muddy for the OCR to translate.)

My love for portability comes partly from necessity, partly from poverty. I am stuck with the Snowball for now because, like it, I am not the best in the world, and am large and awkward. I am trying to kludge together a “digital nomad” system that is workable. So… while I temporarily have access to a desktop system with Audacity, that won’t be the case forever.

The Zoom looks marvelous, but again… poverty.

I might be able to spruce up the system some with a powered USB hub, if that would help. Is either of my two noise problems potentially solvable by a setup like this?

Is either of my two noise problems potentially solvable by a setup like this?

Both of your noise problems would be helped enormously by you getting louder. You didn’t comment on how far from the microphone you were.

Also, are you using the little Snowball desk mount?

If you have chronic low volume, you can help quite a bit with microphone placement.

Pile up books or something (remember books?) so the microphone is just a couple of inches from your left cheek or mouth corner (still pointed to you). Announce more. You should be able to get the Audacity bouncing sound meter to bounce a lot higher than the average -20dB in the test you sent. The background noises will stay the same volume almost no matter what you do and it’s our job to make you a lot louder.

After fighting frying mosquitoes for weeks, we determine the best way to fix it permanently is change the computer or greatly upgrade the microphone. That’s when someone wrote Mosquito Killer. I forget who and they didn’t sign it.

So cut another similar test with the front of the microphone (opposite the USB connection) a lot closer (but not straight in front). Pick something theatrical or sinister. “This is a test” is only going to take you just so far. We tell people to recite the cereal box or milk bottle, but I want to hear some real narrative. Don’t forget to leave the 2 second silence at the front.

You did write and publish something, right? That’s why we’re doing this?


Results are in from the grown-up computer. Are you doing something during that two seconds of silence at the head? The mosquitoes are not the only sound in that portion. You can’t breath heavily, swallow, shuffle or anything else. Freeze and hold your breath.

If it’s additional machine noises, this may get a lot more interesting.


There is one interference tone running through your performance. I surgically got rid of it and was able to pass ACX with much more gentle processing.

This is where I pin that on noises from your computer fan, but correct me, there is no computer, right? How are you reading the script?

Any other fans or things that can make low rumbly noises? It’s 118Hz if you’re counting. If you’re in the US, that doesn’t correspond to any common electrical hum or buzz.

How about lights? What kind of lights do you have in there with you?


I’ve attached the file of me remaining perfectly still before speaking. I set the Snowball off at an angle as you suggested and tried a more dramatic tone.

There was some audible machine noise in the distance outside, as if a prop plane at a great distance. (Thankfully this was recorded late enough that being on BWI’s flight path didn’t matter.)

There’s a power strip in the room that’s feeding several electronics, but I don’t think any were active. I can eliminate that in future, I’m sure.

No lights were on, and the only nearish appliance was a deep freeze five or so meters outside the room.

I’ve got the Snowball and isolation shield up on a box; I remember books, including the numerous books on writing and a small occult library, all left behind with the house. So, box it is. It’s at an OK height, though I still have to crane forward a little bit to be on what I think is the right level with the mic.

And yes, I have some writing (other people’s) I’m trying to get done, although one largish contract cancelled on me because I was taking so long. Getting this recording situation sorted out is the latest of several troublesome delays.

latest of several troublesome delays.

This recording at home thing is harder than it seems. If you believe the ads, just buy their microphone, set up on the kitchen table and start cranking out the high quality work.

We wrote ACX-Check as a convenient guess on how ACX’s Robot automatically inspects new work. You can cycle through two-week submissions to ACX and have it fail, or quickly run ACX Check at home and make corrections right away…if possible.

I know where BWI/BAL is. I lived in College Park. Can you hear planes going over? That’s going to be a challenge. We have had posters in mild shock with a list of appliances that had to be turned off to meet the background noise specification. That’s the killer measurement. We publish an ACX Mastering Suite of tools that automatically set Peak and RMS (Loudness). Noise is the killer and as a rule, you can’t solve it in post production with software.

I have a tiny, very quiet third bedroom that has no echoes and I can meet the noise specification without too much trouble. I put Mr. Wall Clock somewhere else for the duration and unplug the music bass cabinet and internet interface, both of which make acoustical noise. Even with all that, it’s best to work at night when street traffic is almost zero.

I’m in the pattern for LAX, but the jets are multiple thousand feet up when they go over. I can hear them if I’m outside staring up when they go over. With field glasses, I can just make out which airline.

have to crane forward a little bit

That’s where the boom microphone stand comes in.

That’s an on-Stage-Stands microphone stand, OnStageStands9701B. It’s light-weight and folds up to store in a corner of the closet.

It allows you to place the microphone about the level of your nose or slightly higher, either directly in front or slightly to one side and frees up space underneath for your script.

That spidery thing on the back of the microphone is the shock mount to keep floor and desk vibration noises away. Those are rubber bands.

The little folding Snowball stand has problems: You naturally want put it on the table in front, right in the line of your breath blasts, it’s usually in your eye-line where you want to read your script, and it’s right there on the table where it can pick up slap and comb filter effects from the flat surface, and vibrations from the neighbors downstairs.

It’s pretty.

I can identify all the problems except that one tone at 118Hz. 120Hz is the natural tone of electronics, lighting, some motors, etc., in the US. I checked it multiple times. It’s not 120Hz, so I don’t know what it is. Typically, odd tones like that come from computer fans. They have no natural speed and can whine or rumble at odd pitches.

There is a sleuthing thing you can do. Make sure the Snowball is set for Position 1, Cardioid and move it around the room and aim at different places to see if the noise level goes up. That’s how I found my bass cabinet made sound even when it wasn’t being played. You should be speaking into the BLUE logo. That’s the “front” of the microphone.


I don’t remember if I posted the two tools.

This is the web page of ACX Mastering.

That’s the exhaustive description. Scroll down to Process. Do Not add or skip steps. It is a suite. A harmonious grouping.

I attached ACX-Check.

Acx-check.ny (9.01 KB)

Thank you, Koz, for more excellent suggestions. There are multiple “noisy” things going on in my friend’s house, electronically speaking. I’ll see if I can’t identify some of the troubling noises using the wandering-microphone method you suggested.

Believe me, ACX check has made my life easier. If only I’d known about it when struggling through my first book…

I realized I didn’t actually attach the file I said I was going to attach. This is attempt #2.

Haha. “Board attachment quota has been reached.” Is there a preferred place online to put the WAV file so others can access it?

Anywhere publicly accessible, but you can post on the forum if you have a mono wav track under about 20 seconds or a stereo wav track under 10 seconds. The forum will not let you post a book chapter. I think the cutoff is 2MB.

There’s also a list of acceptable file formats.

The trouble with hosting services is you as an account manager can’t always tell when a casual visitor can “see” the works or not. For us foreigners, it may start asking us to start an account or log in. Then we complain on the forum and then you go in…etc. Much quicker to post a short clip on the forum.


I kept chopping it down but the “board attachment quota exceeded” message kept popping up. That’s a board admin issue if my google-fu is strong enough.

Soundcloud link to the chopped WAV (two seconds of silence at the beginning, with an immediate cut thereafter to the reading):