Topic: What does an overloaded mic sound like?

[connloyalist]

I have been asked to record a band. It's a bit difficult to describe their format, but they are 4 trumpets, 4 trombones, 4 baritones (2 upright and 2 with bell front), snare drum, bass drum. No amplification. As it happens I saw them in action today and I suspect they might come a lot closer to the maximum SPL of my microphones than I have experience with. The mics are rated at 143 dB and I don't believe this group is quite that loud (fortunately I did have my hearing protection with me) but it made me wonder:

What does it sound like when the sound level exceeds the mic's maximum? I assume it does the mics no permanent harm? Is the maximum rated sound level of a mic an abrupt thing or does the sound start deteriorating as it gets closer to that number?

Regards, Christine

[mr qpl]

look on utube with that search, you'll find plenty of examples

here is a link to a db chart, if your mics are correctly powered, it is really doubtful that they'll overload at that spec.  might overload a recorder, though. list the gear you are planning on using and there will likely be some reccomendations here

http://www.gcaudio.com/resources/howtos/loudness.html

[waltmon]

I stealthed the Cult with 184's and discovered the overload phenominon...lol.  The were running a huge stadium PA in the Theater. Thats when I picked up external attenuators whenever I taped metal or any othe music where excessive loudness was a concern. Audio Technica has a great attenuator.

  The 184's are pretty hot anyway, so Id use the attenuators fairly often.  Made some killer MMW and Mule recordings that way.  Hope this helps.

[DSatz]

In general, with high SPLs and professional-quality condenser microphones, the inputs of your preamp, mixer or recorder are probably more at risk of overload than your microphones are.

143 dB SPL is just physically intolerable. If your band was producing levels like that "out in the air" (rather than in the bells of their instruments), its members would all have a disabling degree of hearing loss as well as severe nervous symptoms before the end of the first set. I doubt they would be able to get through a set. If you're exposed to "just" 110-115 dB levels for more than a minute or so, you'll be in trouble with your hearing for at least a day afterward, if not permanently. The whole NY Philharmonic never gets that loud even with all guns a-blazing.

Decibels are an exponential scale, not a linear/additive one. Each time you add 3 dB, you double the power. The curve just keeps on rising. Remember the story about the man who asked for one grain of wheat for the first square of a chessboard, two for the second, four for the third and so on? Well before the final square was reached, he would have been owed more than the possible amount of wheat on the whole planet.

Just as a point of reference, the loudest sound I've ever knowingly recorded was with a mike about one foot away from a trained operatic soprano (one who sings at the Met here in NYC) performing a special vocal exercise in the high register, and that was 121-122 dB SPL. It was a master class situation; she and the teacher worked their way up to it gradually, and as the final stage of the exercise the teacher gave the singer the starting pitch, and the singer kind of steeled herself for a few seconds and then did it, and the whole master class broke into applause. The 121-122 dB part only lasted less than half a second, but it was felt throughout the hall.

Brass instruments can get a few dB louder than that, but the only thing that could get you into the possible 130+ dB range would be VERY close miking. If you're recording the band as a whole (not spot-miking each instrument separately and mixing down), you won't be close enough to any one instrument to get more than (I'd wager) peaks of 110 dB or so.

--best regards