Complete newbie and recording an audiobook to ACX


I am desperate for any help Ican get following a series of setbacks in recording an audiobook to ACX.
I have two primary issues:

  1. Id like to ensure as far as possible I am definitely going to meet the requirements before I record another 16 hours of audio… I have a secured a noise proof studio and am working with the recommended rode Nta-1.
    The recording needs to measure between -23 and -18 DB RMS (not even sure what rms is?!) and have peak values of -3, with a maximum noise floor of -60?
    From what I’ve read in forums -60 is very hard to achieve, but I’m working in a completely noise proofed professional studio?
    And how do I ensure the volume falls consistently between -23 and -18?

  2. since I’ve switched microphones I’m now picking up a high pitching whining sound intermittently, particularly if I hit the table or likewise- possible vibrations off something? I’ve read a lot about feedback too- what are the obvious things I should check?

Would be so so grateful for any help,

Id like to ensure as far as possible I am definitely going to meet the requirements before I record another 16 hours of audio…

Ask them if they will allow you to submit a sound sample instead of several gigs of damaged show files.

(not even sure what rms is?!)

Root Mean Square. It’s an approximate measure of loudness. The important measurement values are: Peak, so brief, emphasized words and sounds don’t overload and get damaged, RMS, so overall volume stays constant from show to show, and background noise level. Fffffffffffffffff.

Yes, it’s rough to hit all of those at once, particularly if you’re trying to record a show with a microphone jacked into a laptop in your home office. That’s not to say you can’t do that, but it’s not likely.

Fill out the info in that pink band at the top of this thread. Describe the computer, the microphone and what you did to make a studio.

And yes, we know what the specifications are.


Oops. Sorry. That doesn’t work on this forum. Tell us the computer, operating system and which Audacity you’re using. All three numbers.


It’s a toshiba laptop, I’m on windows and it’s audacity 2.0.6

I have connected the laptop to a Scarlett focus rite 2.i2 interface and then got a brand new xlr cable to the new ride nta1 mic. Using headphones for playback? The booth itself is a professional voice over recording suite - soundproofed, it just has no equipment in it x

We can’t guarantee, but we should be able to get you in the right ballpark.

Your setup sounds good - particularly having a dedicated booth for the job (the recording environment is really important).

That does not sound good.
How is your microphone mounted? Do you have it in a shock-mount on a sturdy floor standing mic stand?

Using headphones for playback? The booth itself is a professional voice over recording suite - soundproofed, it just has no equipment in it

I may know where your whine is coming from. You’re in feedback. You do need headphones even in the studio.

The microphone should be isolated from the table or floor.

I made a shock mount out of plumbing supplies and post office rubber bands. It works a treat.

Next cycle, post a little bit of the sound you’re getting. Erratic whine could be coming from anywhere. There are conditions where USB can do that.


The NTA-1 came with a shock mount which is what I;ve been using, and I have a stand too- though this is leaning slightly on the table to counterweight the microphone (otherwise it seems like its going to fall forward)

I’ve been using headphones, unplugging them whilst recording and plugging back into monitor- just inmc ase this was the source of the feedback.

Here’s a sample of it, as I say it seems to come and go with the slightest vibration?

I’m not sure that I’d call it “ringing”, but it is certainly picking up vibration.

As an experiment, move the mic stand so that it is not resting on the table (adjust the boom arm if it has one to ensure that it does not fall over).
Does that make an improvement?

You have a hideous amount of very low frequency vibration and rumble. I can make it go to zero with Steve’s “LF Rolloff for Speech” plug-in for Effect > Equalizer, but you’d be much further ahead if you suppressed it at the microphone or mixer. I need to step away for a minute.


The microphone is an NT1-A, not NTA-1 and it’s Rhode.

The microphone has no provision to “roll off” the extreme low frequencies. It’s going to relentlessly capture whatever is in the room. The 2i2 (not 2.i2) is not a mixer and has no provision to equalize or change frequencies, either. It’s just a digitizer.

Now it’s messy. Any performance is going to compete directly with that rumble unless you get rid of it. Shure makes an in-line rumble filter the A15HP.
You can plug that in between the microphone and the 2i2.

You can also do it in post production the way I did it, but that means all your level meters and indicators during the performance are going to be wrong.

My mixer has provision to remove rumble on a button (attached). It drops everything below 80Hz.

I can’t find the original rolloff plugin, so I exported mine (attached: LFRolloffForSpeech.xml)

Import that into Effect > Equalization and run the Length control all the way to the right.

I’m doing that on a dead run. Let me know where you get stuck.

LFRolloffForSpeech.xml (453 Bytes)
Screen Shot 2015-01-09 at 10.50.16.png

Because of the way that sounds (you need a terrific sound system to be able to hear it) I’m guessing you live under an industrial building air conditioner or something similar. This is typically not something you can get from a refrigerator or vacuum cleaner.

If you are already using your shock mount, then it’s probably not coming from the desk or floor. It’s in the air in your room. Are you next to a freeway/expressway/motorway?

Nobody I know would dream of shooting voices with a flat studio microphone like you have. Singing, maybe, but not straight speech. It’s an unquestioned terrific microphone, but maybe not appropriate in this case, at least not without helping it a little. I know how this sounds, but it may be too good.

If you say you’re recording in your studio, that should have resolved the rumble…?

This could be an Alice in Wonderland problem.


I’d have to disagree :wink:
There is a review of the NT1-A here:
Yes it is likely to need a bit of bass roll-off, but there shouldn’t be that amount of rumble going on. My current theory is that it is vibrations being conducted up the mic stand through contact with the table. The question remains though, why is the spider not doing it’s job?
Question for Gembo85, where is the mic lead? (describe in detail or post a photo).

See attached. My first inkling of advanced trouble was my speaker grill cloths slapping.

I’ve known people who bought “ideal” microphones under the impression they were workhorses. They were wrong. The microphones spent more of their time in a polished display case than they did on the job. The most popular microphone on earth is the SM58, anything but flat and the studio microphones that “made love to your voice”, the Neumanns, Sennheisers, etc, aren’t ideal/flat, either. How “not flat” they are and how they got there are jealously guarded secrets.

9Hz is a scary frequency to have in abundance.

That’s Lorry Droppings.

Screen Shot 2015-01-09 at 13.55.37.png

In a heroic effort to find something good, If your system will pass 9Hz, it will record any performance you put in front of it.

You can totally have noise coming up the microphone cable. Put a 1/3M loop in the cable and hang it from whatever is holding up the shock mount.

Something else you can try: Pick up the microphone and hold it in your hand with a sloppy cable on the floor or desk and make a sample recording that way. I understand we’re going to get skin and handling noises, but if that 9Hz stack drops to nothing, then the problem is coming up the mount or desk.

All I did to get that pattern was drag-selected the portion between 2 sec and 4.5 sec (attached) and Analyze > Plot Spectrum. Select similar settings as those in the analysis picture.


You understand that if the rumble signal doesn’t vanish when you hold the microphone, then it’s in the air of the house. Frequencies lower than about 20Hz can go through walls and around corners.

That’s the land of earthquakes. People experiencing a quake for the first time look out the window to see the heavy truck/lorry going by.

No lorry. Sorry.

Screen Shot 2015-01-09 at 14.17.29.png

Im so sorry I’m such a dunce with this stuff. Have the studio space booked for two more days so am unlikely to be able to buy any new kit in that time frame, if there is a way around it.

To clarify your points Koz (I’m so sorry!!!) are you identifying two seperate problems? Is there the vibrations that are the (not really ringing but whiney) sounds when something is hit ASWELL as a low frequency rumble? Or is that the same thing?

If the low frequency rumble/vibrations are a seperate issue, could the issue be here that I have a noisy computer? During the recordings of the actual vocals I shut a sound proofed door on this, but chose the above extract, with the laptop in the same room, to demonstrate the high pitched noise?

This is sound for dummies I realise- I’m leaving it to the experts next time!

I shall move the mic stand away from the table first thing on the new batch. In the meantime:@

Here is a clip with some vocals on it: could you let me know if the same problems are exhibiting themselves? And whether or not its the same fix?


I’m not at the studio at the moment, will take pictures of the set up tomorrow and upload them.
I am panicking!!
The voice over studio is really top of the line BBC quality, and professionally noise proofed. It is a professional recording studio I;ve managed to wangle my way into, so it must be my equipment / use of the equipment rather than the space itself :frowning:

Also- the Rode mic was the one recommended by ACX… the whole reason I bought it?! Would this not indicate that it lives up to the standard required and its my misuse of the mic rather than the thing itself?

my misuse of the mic

There’s another variable in there. Environment which is why you got the studio. There’s nothing wrong with the microphone. It’s a perfectly delightful mic similar in quality to the microphone I used on this shoot.

… and the only difference is I was using a small sound mixer on the shoot and I was restricting the rumble and low frequency sounds. I was also in a known good, working room. That’s a soundproofed conference room that had been hosting successful sound shoots for years. I found out that the company who was in the building before us also used it for sound shoots. So I didn’t do anything original.

We’re being a little fuzzy about this because I don’t think we heard the same sound damage you did. Once I got rid of the rumble, it sounded like a microphone in a room with somebody drinking a glass of liquid.

I want to critically listen to anything you posted in the last couple of hours when I was out. It’s not unheard of for a producer to be prostrate with grief over a sound problem none of the rest of us could hear.


There’s nothing wrong with anything on that list, except the Blue Icicle digitizer. We’ve had troubles with simple microphone digitizers like that one. Turn the volume up a little in this clip when I stop talking.

The MDR-7506 headphones can be seen on every hollywood movie shoot, etc.

Please note that none of these lists sell you a computer or other stand-alone recorder. Wouldn’t that complete the turn-key operation?

As we go.


“…on the many colours of red, orange, gold and brown in his hair.”

I think I’m going to need to lie down for a minute.

I applied Steve’s filter to get rid of the grumble and I reduced the peak sizes to -3. If this clip doesn’t make certification, it’s not far off.

My WAV version doesn’t fit as a forum posting.