Sample Analysis Please!

Hello everyone! First off, thank you SO much for this forum. I’ve been lurking around, and have already learned quite a lot. I’m very grateful. I’ve attached a raw WAV sample, and wonder if you pro’s wouldn’t mind taking a look at it, and giving me any pointers/tips? I would greatly appreciate it. Thank you!

You’re a lot closer than most people get. There is a stunning amount of sub-sonic noise. Earthquake/thunderstorm stuff. It responds nicely to Steve’s vocal filter.

This is my local copy.

Download and unzip it to LF_rolloff_for_speech.xml. Install it in the Audacity Equalizer tool.

Adding Audacity Equalization Curves
– Select something on the timeline.
– Effect > Equalization > Save/Manage Curves > Import
– Select LF_rolloff_for_speech.xml > OK. (it won’t open the ZIP. You have to decompress it)
– LF rolloff for speech now appears in the equalization preset curve list.

Then apply it.

LF Rolloff (rumble filter)
– Select the whole clip or show by clicking just above MUTE.
– Effect > Equalization: LF Rolloff for speech, 5000 Length (approx) > OK

All I did was “roll off” all the rumble. I ran ACX-Check and it passes.
Screen Shot 2016-07-27 at 6.14.45 PM.png
You can run ACX-Check, too. It’s a plugin that appears under Analyze.

It automatically checks for the three sound qualities that ACX looks for when you submit your work.

Actually, the automated robot does that. If that passes, the work goes on to Human Quality Control.

Describe your studio.


can you explain what you mean by subsonic noise? I’m still very new to all this…

As for my studio, I’ve got a desk set up in a closet under my stairs. I’ve got acoustic foam on the wall in front of me, and to my left, with the door immediately behind me. The area to the right is open right now, but I’m going to hang things like winter coats, etc there to help. I’ve got a Rode NT1A with a pop filter attached to this boom: It is plugged into a Scarlett 2i2 interface, which runs to my lap top. I’ve got a blanket on top of the desk, and the laptop is sitting on top of two inches of foam.

“Subsonic” means “below sonic”, which is a term usually used in the context of the speed of sound (a subsonic aircraft), but koz is using the term in relation to the frequency range of audible sound, ie “infrasound” (sound below 20 Hz).

As shown below, there is a strong peak at about 11 Hz.
window-Frequency Analysis-000.png

Sometimes microphone systems can do that. It doesn’t necessarily mean you’re experiencing an earthquake.

Have you been through an earthquake? That’s a classic event where everything including the air is moving, just not fast enough to hear. “for some reason, my wineglass just fell over.” Also see the thunderstorm which you can barely hear, but your windows start rattling. Growling Cathedral Organ notes that make your shirt move. And, etc.

But that’s solvable with a simple filter. I don’t think you can easily get rid of it during the performance, but it’s possible. Can you move the microphone, 2i2 and computer outside and make a recording? I understand it’s going to be noisy, but if it’s environment, that peak will go away and it may be possible to adjust the studio so you don’t need the filter. Here’s a suggestion how to shoot a sound test.

You have a vibration mount on the arm, so it’s not floor or desk vibration, but it could be air vibration if you’re recording over an air conditioning pump or other motor. Again, you can’t hear this sound (so technically, I guess, it’s not “sound”)

I bet you’re asking yourself, “If it’s not sound, who cares?!?”

The way ACX measures noise includes infrasonic sound, and your raw clip will not pass.

I’m more concerned with the announcing in a rain barrel sound. The studio worked in the sense that you have almost no background sound or noise, But it does sound like you’re announcing in a small elevator.

My metaphor for the ACX recommendation is telling somebody a story over cups of hot tea in a quiet kitchen. How may other people can you get in the room with you? It has to sound like a larger room, or better, no room. The existing bare walls are also giving you a false announcing boom sound. “NBC Radio News on the Hour…” No. I bet you don’t normally sound like that.

A poster used to go to her open-plan office after hours when they turned the noisy air handlers and ceiling lights off and announce there. In that case the super large room worked well.

Finish the sound treatment and make another test. Did you put anything on the floor? Who made the sound panels?


I really do try and stay away from theatrical quality judgements. I leave that up to you, ACX and the client, however, this is an aural effect you can’t change by changing your announcing style or emphasis. That makes it a physical or electrical problem.

The object of the studio and recording system is to become invisible.


I’m trying to determine what you mean about sounding like I’m in a small elevator. The space I’m in is quite small. I tried several recordings to try to learn the software before reading here, trying some of the things said here, and uploading that sample. It sounds FAR better to my ear at least than any of the others. Can you try to elaborate on what you mean? Also, that’s pretty much what I sound like…

Can you try to elaborate on what you mean?

I’m being picky. You mentioned you were going to add additional sound absorption in the form of winter coats and heavy clothing. Highly recommended. Go for it.

After I got rid of the rumble with Steve’s filter, I still had a performance with more bass boom than is normal. That’s typical of announcing in a box or rain barrel…or a closet with not quite enough soundproofing.

But if you’re happy with the sound, that works for me. The work passes ACX testing with a simple sound filter. You can take up production details and delivery with ACX and the client.

Who did make the foam sound panels?


These are the panels I got:

I’ll add the sound proofing in the form of winter coats this weekend and see how that goes. Thank you for all your input!

I did miss a step. How are you listening to the work? A good microphone, stand, soundproofing, preamp, etc, etc is half of the studio. Good speakers or headphones is the other half. If we’re hearing stuff you can’t hear, maybe you’re not listening critically enough.

Low pitched sounds are difficult. I took a picture for illustration of a digital connection.

I used the Mac earbuds because they were convenient and pretty. They are terrible headphones and I would never use them for production.

Most of Hollywood uses these:

The 7506 goal is different from entertainment headphones. The goal of these is to show you when you’re doing something wrong.



Cool. Terrific panels. Did you stagger them, horizontal, vertical, horizontal, vertical…?

Shucks. I had a picture of that here…somewhere.


I can’t believe I found it…
Screen Shot 2016-07-06 at 6.46.12 AM.png

I did not stagger them. Do I need to? And as for headphones, I have a relatively cheap pair of Fender over-the-ear headphones.

I did not stagger them. Do I need to?

Probably not. It’s customary to do that with the goal of breaking up sound reflections in every way possible. I suspect if someone did change from regular to irregular, they wouldn’t notice any difference. But then, I don’t know anybody who’s tried.

Please note in that picture the heavy drapes on the left. That’s not accidental.

Irregular anything is good. The company used to have a studio with very little soundproofing, but I cranked several successful recordings through there. What it did have was non-parallel walls and ceiling. The ceiling was closer to the ground on one side of the room than the other. The walls were not square. If you laid a square and proper rug in the room, it wouldn’t fit, or it would only fit against one wall and not the other. You wouldn’t think that would make a big difference, but the effect of not having repeatable echoes was surprising. Flynwill was the engineer on that and can comment if you’re interested.

I pulled several recordings out of a small room with storage boxes in it. Floor to ceiling transaction and production records in boxes…all irregular sizes and shapes. Sounded fine until somebody needed the room for an office. The boxes and I had to go.

Fender over-the-ear headphones.

Model number? Speakers or sound system?


If you look at the spectrogram***** of your sound it has many horizontal slices missing …
smcompton's spectrogram has horizontal slices missing.png
Those missing slices are caused destructive interference from the sound reflecting from the nearby walls.
The missing slices are what gives it the in-an-elevator sound, [similar to a comb effect].

If your voice is being played back in your earphones as you speak, and can be picked up by the microphone , that can also cause the comb-effect. You could try recording once with the headphones disconnected just to see if that is causing the problem.

[ ***** you’ll have to turn up the “window size” of the spectrogram from the default setting of 256 to 2048 to see the slices ]

Using very precise equalization it is possible to make it sound less comby …

but the only practical solution is to change the acoustics of the room.

See? I’m not making that up. You can improve the quality of your voice with a little more acoustic mush in the room.


I see. Man, you guys are awesome. I’ll be adding “acoustical mush” this weekend then, and I’ll be sure to add another sample once that’s done. My goal is this: I want to tack up thick-ish moving type blankets on the “ceiling” (the bottom of my stairs). In addition to that, I want to put one up on the door to the closet, which is immediately behind me when recording. Lastly, to my right where the closet goes further under the stairs, I plan on putting up a bar so that we can hang winter clothes/coats (with the added benefit of acoustics). Thoughts?

That’s basically how I did it.

Those walls are double blankets. You can see the second blanket peeking over the top in the back. Note the folded blanket on the floor.

That’s me shooting voices for an animated production.


awesome, where did you get your blankets?