how much power can a little condenser mic take? - Page 1
Forum section: electronics / beginners

author: Capernicus
author_rank: Frequent Contributor
timestamp: October 16, 2021, 06:41:35 am
content: I've got a system for a megaphone, and it looks like I need 800mW, to go from the microphone, into my amplifier.Will 800mW blow a condenser mic?I mean one like this->https://au.element14.com/kingstate/kecg2740pbj/microphone-miniature-electret/dp/1299885?gclid=CjwKCAjwzaSLBhBJEiwAJSRoktb0JIx-EwXirrsTLD2rjfobXcJB-gIDI-fPao3Y3FanpY_Gc0lRPRoC8KAQAvD_BwE&mckv=_dc|pcrid|501152839127|pkw||pmt||slid||product|1299885|pgrid|123988903131|ptaid|pla-293946777986|&CMP=KNC-GAU-GEN-SMART-SHOPPING

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2021, 06:53:49 am
content: how much is sound level in dBA?

author: Capernicus
author_rank: Frequent Contributor
timestamp: October 16, 2021, 07:01:17 am
content: Sorry, I dont know how to convert watts to decibels.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2021, 07:22:27 am
content: if I'm not mistaken, 0.8 W is about 10*log(0.8/1e-12) = 119 dB SPLUsual electret condenser microphone likethis onehas acoustic overload point at about 130 dB SPL, so probably it should work ok even at very close proximity to the source. But I don't see such specification in your microphone datasheet, so I'm not sure...

author: Capernicus
author_rank: Frequent Contributor
timestamp: October 16, 2021, 07:26:27 am
content: thanks alot!

author: CaptDon
author_rank: Super Contributor
timestamp: October 16, 2021, 01:39:42 pm
content: No condensor mic puts out 800mw. Maybe your spec meant 800mv which couldbe more typical. Even that figure is high for most powered condensor mics.

author: TimFox
author_rank: Super Contributor
timestamp: October 16, 2021, 02:31:09 pm
content: Start over with the correct units:dBA is a measure of the sound level (pressure) hitting the microphone. It involves a frequency weighting factor applied to the physical measurement in dB SPL, which is dB over a reference level of 20 uPa rms pressure amplitude. The 130 dB SPL overload point (into the microphone) quoted above is a very loud sound level, usually considered painful, that can occur at rock concerts or near very loud equipment.As stated above, microphones do not put out anything like 800 mW (almost a watt). That level is typical of a somewhat low-power audio amplifier output to drive a small loudspeaker. What is the exact statement or specirfication that tells you "I need 800 mW, to go from the microphone, into my amplifier"?The data sheet for your low-cost microphone states a sensitivity of -40 dB with respect to 1 V/Pa (output voltage divided by input sound level) so the output voltage at 1 Pa rms would be 40 dB below 1 V, or 10 mV. 1 Pa is about +94 dB SPL. Therefore, at 130 dB SPL (no specification of overload in the data sheet), the output voltage into high impedance would be 36 dB higher, or 630 mV.(The above arithmetic was done while coffee is brewing--please check it.)

author: dmills
author_rank: Super Contributor
timestamp: October 16, 2021, 02:47:00 pm
content: -40dBV is 10mV not 1mV! Which would be fairly typical of a condenser of the usual sort.I would be very surprised if any audio modern amplifier was specified as power transfer on the input, they are almost all voltage driven.

author: TimFox
author_rank: Super Contributor
timestamp: October 16, 2021, 04:04:28 pm
content: If you are referring to my post immediately above, I explicitly stated: "40 dB below 1 V, or 10 mV"1 Pa rms is a reasonable sound pressure level, far above the threshold of hearing and well below pain level.

author: Terry Bites
author_rank: Super Contributor
timestamp: October 16, 2021, 04:32:13 pm
content: Sound level (SPL) in dBm is measured at a specific distance between source and mic. Usually 1m. You can't calulate it from an ouput power as such.You can get a phone app to give you a ball park figurehttps://play.google.com/store/apps/details?id=com.keuwl.splmeter&hl=en_GB&gl=USI'm sure there is one for iphones too, for a million quid or so. Fapple!

author: TimFox
author_rank: Super Contributor
timestamp: October 16, 2021, 05:05:03 pm
content: Sound pressure in dB SPL is the value directly at the microphone input, referred to a reference pressure amplitude of 20 uPa rms. Sometimes, this is specified directly in dB with respect to 1 Pa instead of the conventional definition of dB SPL from a nominal threshold of hearing.For a loudspeaker driven by a given electrical power, the dB SPL at the listener or microphone input is a function of the distance from the source (loudspeaker), and should be specified by the loudspeaker manufacturer."dBm" is a measure of power, referenced to 1 mW, not normally used to measure sound level.Sound is a longitudinal wave (along the direction of propagation) characterized by the pressure (deviation from mean atmospheric pressure) and velocity (actually, flow rate). The product of the pressure and velocity gives the power and the ratio is a function of the medium (air, water, etc.). The details are complex: see a good textbook.

author: radiolistener
author_rank: Super Contributor
timestamp: October 16, 2021, 10:54:50 pm
content: Yeah, sound power is measured in Watts and it doesn't depends on distance, because sound power is specified for a sound source.Sound pressure level is measured in dB relative to 1e-12 W (20 uPa) and specified at sound receiver. It depends on the distance from source because there is attenuation which depends on the distance.0 dB SPL = 20 uPa = 1e-12 W/m2 is the minimum sound pressure level which human ear can detect.130 dB SPL is a very loud sound. For comparison:100 dB SPL is about the sound level in the helicopter cabin.160 dB SPL is about the sound level at 1 meter distance from shooting shotgun.180 dB SPL is about the sound level at 0.25 meter distance from shooting shotgun.Prolonged sound pressure level above 120 dB SPL can cause harm to a human ear.The interesting fact is that maximum sound pressure level is limited by atmospheric pressure of air which value is about 100 kPa, so the maximum possible sound pressure level at atmosphere pressure 100 kPa is:Pmax = 20*log(100 kPa/ 20 uPa) = 193.9794 db SPLHigher sound pressure level is not possible because air pressure of environment is not enough to transfer so powerful wave.So, the dynamic range between lowest sound pressure level that human ear can detect and maximum possible sound pressure level in the air at normal condition is 193.9794 dB. And there is interesting fact is that such dynamic range requires 32 bits DAC/ADC:ENOB = (193.9794 - 1.76) / 6.02 = 32 bitsThere is also frequency limit for the sound, because sound wavelength should be at least twice longer than the distance between molecules. For air in normal condition the distance between molecules is about 100 nm and wave propagation speed is about 335 m/sSo, the maximum sound frequency limit at normal condition air atmosphere is about:f = 335 / (1e-7 * 2) = 1.675 GHz

author: Capernicus
author_rank: Frequent Contributor
timestamp: October 17, 2021, 07:21:35 am
content: I've just advanced my system and maybe ill need less than 800mW. See what happens, but as far as I know microphones dont work unless you supply the power to them.

author: TimFox
author_rank: Super Contributor
timestamp: October 17, 2021, 01:49:29 pm
content: At what point in the system are you requiring or measuring the 800 mW level?The microphone you linked to is a capacitor/electret microphone, which requires power for the small amplifier included in the package.Other microphones, such as "dynamic" microphones with a moving coil inside a permanent magnet, do not require DC power and output AC voltage.