I finally got a little test clip...

If it really is a constant drone, it’s far more likely to be the interstate. If it were aircraft you would probably hear it as individual sounds coming and going. I used to live about half a mile from the infamous Pasadena Freeway. It has vintage concrete paving, the kind with expansion joints every 40-50 feet, so all the cars go clop-clop…clop-clpo…clop-clop as they pass, during the day all of the clop-clops merge together into a more or less constant drone. But very late a night when traffic gets light you could distinguish individual vehicles and hear them until they are several miles away.

Yep that’s there. “Generate” → “Noise”… just pick your color white, pink or brown(ian).

Well actually, I wasn’t thinking about my particular case, but for would be narrators in general. Perhaps it’s not too feasible for ACX to check for that type of thing, but it does seem to me like some of those narrators, without the help of the Audacity forums and resources, might give up if they bought some decent equipment, put up some sound absorbing materials throughout their studio, follow the ACX recommendations to a “T” & still get rejected.

Somewhere on the ACX website they give some tips on how to quiet your “studio”, but they also said somewhere that sometimes it just can’t be done there, that you need to move your studio elsewhere. That’s probably true, but I imagine that would be a deal killer for at least some people, perhaps even most people looking into it.

I’m saying that it would be a shame if people gave up at that point, and the cause of their problem was noise at frequencies which could not be heard anyway. Would those infrasonic frequencies mess up .mp3s for audiobooks, btw?

In my case, the remedy was relatively easy to fix, but only with the knowledge of what was causing the problem and how to filter that out. I didn’t have that knowledge, and probably most laymen wouldn’t know that either. I haven’t seen any How To’s about such things on the ACX site, and tend to doubt that they have them. I was just fortunate that I found Audacity and that the experts on the Audacity forums showed me how to find that problem and correct it. Those who bought the software that many recommend, probably weren’t as lucky, unless they found their way over here anyway.

I haven’t seen any How To’s about such things on the ACX site,

No and that’s precisely where we had our little discussion. We live in details and specifications and they tend toward broad overviews and generalities.

I haven’t found it yet, but we have actual technical tests to make sure your performance is in the ball park. I have never seen anything like that on the ACX system. I think you’re supposed to submit and pray.

If you watched through some of the videos, there are sections devoted to the construction details of your sound proof booth. Like, of course, you have one. Actually, Ian on the forum (also in LA) does. That’s how he got his first novel published. I have a particularly quiet third bedroom and that’s how I shot my sound tests.

It’s not popular to say this, but there are setups and locations that will never produce ACX compliant sound files. Everybody on the forum shows up with the idea that we’re going to rescue their performance. All the tools we use to help do that are featured in a lecture slide called “Tools to never use.”

Would those infrasonic frequencies mess up .mp3s for audiobooks, btw?

My opinion is yes. MP3 encoding breaks up a sound performance into characters, sounds, overtones and harmonics. Then it deletes the quiet ones and puts the show back together. So no, it doesn’t just make the show muffled. That was the trick. Few people can tell they’re listening to a compressed show until you either screw up the compression or directly compare the show to the original.

If you have significant trash too low or too high, those sounds are directly competing with the high quality actual performance for compression attention. If you have rumble, for example, and it’s louder than the overtones of the violin you paid a lot of money for, you now have a lower quality violin and perfect rumble.


I may have found the answer to my own question. Per a Wikipedia article on infrasonic sounds, that not only did the ability to hear sounds below 20 Hz vary somewhat, but that a significant number of people are made uneasy or even fearful even when they couldn’t actually “hear” the sounds:

"One study has suggested that infrasound may cause feelings of awe or fear in humans. It also was suggested that since it is not consciously perceived, it may make people feel vaguely that odd or supernatural events are taking place.[33]

… The participants were not told which pieces included the low-level 17 Hz near-infrasonic tone. The presence of the tone resulted in a significant number (22%) of respondents reporting anxiety, uneasiness, extreme sorrow, nervous feelings of revulsion or fear, chills down the spine, and feelings of pressure on the chest.[34][35]

…Tandy was working late one night alone in a supposedly haunted laboratory at Warwick, when he felt very anxious and could detect a grey blob out of the corner of his eye. When Tandy turned to face the grey blob, there was nothing.

The following day, Tandy was working on his fencing foil, with the handle held in a vice. Although there was nothing touching it, the blade started to vibrate wildly. Further investigation led Tandy to discover that the extractor fan in the lab was emitting a frequency of 18.98 Hz, very close to the resonant frequency of the eye given as 18 Hz by NASA.[36] This was why Tandy had seen a ghostly figure—it was an optical illusion caused by his eyeballs resonating. The room was exactly half a wavelength in length, and the desk was in the centre, thus causing a standing wave which caused the vibration of the foil.[37]…"

I think we’re playing dueling posts. I need to come back and read yours.

All perfectly correct. I live near an airport and when a Very Large Jet goes over, you can see ripples in your ice tea.


Also see: thunder, earthquakes, etc. Earthquakes are a particularly good example of this. The dog goes supersonically nuts and the cat hangs from the ceiling just before you can feel the building move. They’re responding to, I think it’s “B Waves” which are subsonic.


Unless you’re like me and have trouble lifting your bass speaker cabinet with both hands, I seriously doubt anything about your sound system will do 15Hz. Much more likely, anything south of 30Hz or 40Hz. The standing joke is that nobody has 60Hz power mains hum. Everybody has 120Hz and up, because that’s what lamp dimmers and motors generate and everybody can hear that.


You have 60 as well, but nobody can hear that. That’s close to “B” on the pipe organ pedals which you can’t so much hear as feel. And yes, those are the ones played during the “Gloria” to impart a feeling of power and exaltation.

And you thought it was the coffee you had for breakfast.


Oh, and to connect the dots. Just because your speaker system or amplifiers or soundcard can’t deal with them, subsonic tones are still present in the digital recording and that’s what the MP3 encoder is using.

That’s why I’m saying they produce “magic” damage. For Some Reason, the quality of the MP3s is worse than it should be.


Thanks, Koz. Interesting stuff. Learn something new every day. Or two or three things.

There’s a lot more to this than I had imagined. I guess that’s why they have sound engineers and so many people dealing with sound on sets and things, rather than some high school kid to just plug it all in & set the volume.

Some people luck out and produce good quality work with no effort. They’re the ones that post YouTube videos on how easy it is prompting thousands of others to try it.

Sound without the pictures is a radio show. Pictures without the sound is a rehearsal.