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Absolute Pressure Sensor For SPL Metering

Delta Prime

Jul 29, 2020
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Hi, would anyone know how to measure decibels with absolute pressure sensor? 10-100hz range. Something similar to
Yes.
I would know,but I'm not anyone.
The energy of sound or Sound pressure level is dependent on the microphone frequency response.
All microphones have one thing in common a diaphragm.
With the appropriate microphone one uses a sound level meter.
The meter itself uses a frequency
weighting curve.
The human ear perceives the same level of sound pressure at
1,000Hz "louder" than at 100Hz.
You won't hear crap at 10HZ but the water molecules in your body would vibrate if the sound pressure level was high enough. You will feel it,not hear it.
Frequency weighting in sound pressure measurement is defined by IEC 61672.
So...do you want to go pro?
Do you want to go hobbyist?
Do you know how to read schematics?
Do you know how to solder?
Would you like to make your own or would you like to buy it off the shelf?
 

hevans1944

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The Russian device the OP linked to is quite expensive. @Movox didn't provide any specifications other than what is described in the link, so perhaps something like this Radio Shack (Realistic) Sound Level Meter would work. I got mine at a second-hand store here in Florida, but they may still be available through sellers on eBay. It has both A and C weighting, toggle switch selectable slow or fast response, 60db to 120db ranges in 10db steps, +6db to -10db D'Arsonval analog meter indication on each range, a battery test position of the rotary OFF-BATT-120db-110db-100db-90db-80db-70db-60db selector switch, an RCA phono jack output, a screwdriver accessible hole for calibration, a built-in microphone, a 1/4-20 tripod mounting hole, and operation from a single 9V "transistor radio" battery.

1700771380577.png

@Movox asked if there were any absolute pressure sensors available to measure sound pressure levels in the range of frequencies from 10Hz to 100Hz. Yes, there are, but you will have to do your own research to find out what is available, and whether or not what is available will suit your needs or wants. It would help us to help you if you would describe WTF you are trying to DO rather than propose some ill-conceived way to do it based on absolute pressure sensors. Do you even know the difference between an absolute pressure sensor and a relative (or gauge) pressure sensor? As @Delta Prime mentioned in post #3, what you might be looking for is a microphone with a diaphragm that converts sound pressure waves to mechanical motion in the frequency range of interest. The types of microphones available are huge, but they all share one common element: a mechanical device that converts sound pressure waves into physical motion. This physical motion is the transducer element of any microphone. The motion is converted to an electrical signal by various means that are beyond the scope of this response, but you must do your own research to discover which microphone best fulfills your needs or wants. And then there is the problem of calibrating and weighting the response of the microphone as function of sound pressure amplitude versus frequency and how fast it must respond to changes in amplitude. There are a lot of things to consider, so please begin a dialog to discuss them.
 
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Delta Prime

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. It would help us to help you if you would describe WTF you are trying to DO rather than propose some ill-conceived way to do it based on absolute pressure sensors

Forgive me...I believe he said [{(WTF) What The Frequency}] was.
Hi, would anyone know how to measure decibels with absolute pressure sensor? 10-100hz range
:)
 

hevans1944

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Forgive me...I believe he said [{(WTF) What The Frequency}] was.
WTF is a meme that appears to be popular right now. I do have some idea of what it means: World Trade Federation, perhaps? Or, What's That Fellow? It is sort of like using BUFF to refer to B-52 bombers. When I was in the service, I was told that BUFF meant "Big Ugly Fat Fucker" but later references said it means "Big Ugly Fat Fellow." I object to this because, like ships that sail the seas, airplanes are FEMALE. Just look at the name of the Enola Gay, the B-29 bomber that ushered in the age of atomic warfare. This airplane was named after the pilot's mother. And B-52 bombers are beautiful, not ugly at all. They are "large cars" though, not to be confused with diesel semi-tractors operating on the highway without a trailer.

It would help us to help you if you would describe WTF you are trying to DO rather than propose some ill-conceived way to do it based on absolute pressure sensors.
So, WTF, loosely translated could mean "What The Fig," or whatever you want it to mean. In context, it means to quit beating around the bush (no connotations, please) and describe the problem instead of describing a solution. If the OP (Original Poster) had a working solution there would be no need to post a question to this forum. So, if the OP decides that they have a solution (in this case an absolute pressure sensor) and are looking for suggestions of exactly which sensor to obtain and how to use that sensor, then the OP needs to do their own homework before posting questions here. This is a hobby forum, not a design bureau. Most responders here expect the OP to have some idea of what they want to do. Many expect the OP to know at least a little bit about how they might do it, but that is never required. So, if the OP doesn't have a clue, they should state right up front that they don't know what they are doing and then ask for advice on how to do it. That's my two cents. Take it for whatever it's worth to you.
Or just drive on by and troll somewhere else.
 

hevans1944

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Or we would be speaking German right about now!
More likely we would be speaking Russian. I tried learning German in high school and in my first year in college. Unsuccessful. Then I tried learning Morse Code and found that my brain doesn't "hear" foreign languages easily. I did eventually learn to send and receive code at around twenty words per minute during my Novice license term of one year, but it was never easy. And I never did learn how to recognize complete words sent at high speed, which apparently is a requirement for "copying" code at speeds faster than twenty words per minute, which is about as fast as I can write by hand. Perhaps if I learned how to copy code while typing, my Morse speed would increase, but I doubt it. I have tried over the years to learn a little Spanish, too, without much success. Perhaps if I had learned a different "milch language" as an infant, or been exposed to a multilingual household while growing up, my brain would have developed a capacity for easily learning new languages. Too late now.
 

Delta Prime

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Thank you for the quote.
Darn it.
I deleted that!
I got to stop thinking out loud.
 

bertus

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Hello,

Have a look at fig. 8 of the following page to, on how to modify a cheap electret mic for SPL measurements:

Bertus
 

hevans1944

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@bertus: Thank you for the wonderful link. This brought back a lot of memories from the 1970s when electrets were first being used as temperature sensors. I was fortunate to be able to "play" with the early electrets, but lost interest after a few years and moved on to other projects. The author of the paper, Rod Elliot, remarked at how well electret condenser microphones performed while being extremely inexpensive. IIRC, these devices were created about the same time that lithographic micro-machining of silicon was being used to create all sorts of spiffy electro-mechanical devices... rate gyroscopes, strain gauges, micro-manipulators and actuators, and of course electret-based condenser microphones. As we all know now, lithographic reproduction of integrated circuits is pretty much "old hat" with features in the nanometer size range, but micro-machining was just beginning to come into its own in the 70s. A similar thing occurred with LEDs (Light Emitting Diodes) but took a lot longer as it took a while to develop from red and yellow through orange, green, and finally blue LEDs. White LEDs took me by surprise, although I was aware of Sony and their Blu-Ray ultraviolet LEDs. It just didn't occur to me to use the UV to excite a "white light" phosphor. Now all manner of programmable LEDs are available for just a few cents each in any currency.

You will have noticed that @Movox is a "drive by" poster, not interested in any sort of dialog concerning his project or what he or she is trying to do. I suspect the question was related to determining safe sound pressure levels for music concerts. These can be quite loud, so some measure of protection (distance) for the audience should be required or at least determined ahead of any performance. The narrow range of frequencies (10 Hz to 100 Hz) appears to coincide with where most of the sound energy is located during a typical "rock and roll" performance.
 
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