New category Sound? Noise floor

This doesn’t seem to fit in Music or Systems.

Today, I measured my noise floor. 25dB steady state, mid day, though I don’t think it’s all the much quieter at 3am. Regardless, I’m not up at 3am so it’s rather moot for me.

I listen ~70dB give or take 10dB much of the time. Structure is 1952 ‘stucco plaster/concrete’, raised oak wood floors. I have stand mount bamboo lam, ported 6" with alum ribbon tweets, and two sealed servo 12"s for the foundation.

What is a reasonably good ratio of ambient noise to preferred volume? or a good background noise level?

45dB sounds pretty darn good.


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You can’t measure 25dB ambient with any consumer level meter…you need a professional meter worth many thousands of dollars before you can believe any reading of 25dB.

I figured it was too good to be true (non calibrated iPhone mic).

I do have a $100 Umik-1 that is better than the mic that came with my Anthem. I should have it out to set delays later this week using REW. I don’t have any MiniDSP gear but I think I purchased the mic from them.

I can assure you that a reading of 25dB using an iPhone mic - calibrated or not - is totally meaningless. Now, if you were using a B&K 2250-S then I would believe it.

Yeah, noise floor is a real problem. In my first house the ancient hardwood floors were so bad, even the cat could make them creak.:sunglasses:


Just for reference, the media room in my suburban house which is in a basement with brick exterior and measured at midnight, and without central air going, measures about 38-40 dB with Umik-1 and Room EQ Wizard. I have a few acoustic treatments with carpeting and wall panels. The AC kicks it up to about 40-42 dB. That’s also with my projector off. I think it is hard to get much below that without serious effort to soundproofing walls and foam all over the room.

I would expect with that construction that 35 dB would be a more typical background.

A truly excellent modern concert hall is 25dB or a bit below. This is strikingly quiet.

In the back room of a wooden house with brick façade in a London suburb at dead of night the level recorded by my fancy weather station is 35db. I have checked it against my actual db meter and it seems pretty accurate.

OK this is a very helpful reality check. As a result I did a review of the noise measurement accuracy of audio apps available for iDevices. Most were rated as rubbish however 2 measured as being very accurate - see:

Could you please venture an estimate as to the minimum dB level that would be believable from an iPhone / iPad mic?

My background is in environmental noise assessment, regulation compliance, and noise control. I have no experience with iDevices in this field at all. Whilst they might be a useful tool in the hobby space, they have no place in professional applications, particularly for compliance monitoring. Anything I might say about the efficacy of iDevices for noise measurement would only be a hunch. If an iDevice measured 35 dB in a quiet room I’d probably believe it. If it measured less than that I wouldn’t.

Thanks, just what I needed to know.

I do not live in the Apple world, but an Android sound meter app installed on my phone gave readings almost identical to my real db meter, When I reinstalled it on a new phone it was -9db down. My conclusion; hobbyist devices should be calibrated against a conforming meter if you want even approximate accuracy.

@davidl - thank you for the info, I loaded the best rated app and took a reading this morning in my music room which I rate as pretty quiet. It appears to confirm (even if it’s not absolutely correct) it is quiet.

@Brodric - agree we have to be careful using all these app things but as general/relative use don’t you think they assist in our exploration- especially if people use the same apps? I know the users device sensitivity will still be an issue.
Did you leave this field to become a helicopter pilot? Moving from monitoring to working in a very noisy environment.

Yes, they have their place in the hobby space, but don’t blindly accept what they say, especially if it measures your background at 28 dB. And yes, flying helicopters was an opportunity not to turn down. Fortunately now I’m done with all of it.

On the other end of the spectrum, many mobile phone microphones are restricted to 90dB or less. This is not the fault of the app and is hardware based, but it limits their usefulness.

Similarly, Radio Shack sound pressure meters and other inexpensive measuring tools do OK for wide-band mid-level SPL readings, but their sensitivity greatly varies with frequency. There are correction curves available online for the Radio Shack meter.

I’d reported an buzzing issue with my P10 and used the app to (I think) demonstrate what I’m hearing, the snapshot clearly shows a spike just above 8Kh. . image

My P3 had a pronounced buzzing noise. It was the re-generator bypass replay. Maybe your P10 has a similar problem. Obviously it shouldn’t be buzzing.

Yes, just sent an email to Mike. Hopefully he can get Lance (tech) to look at it.