Re: Mike element

iz oos

Tnx Jerry for this valuable explanation in plain English. I learnt a lot from it. Hope this topic could become a question in the FCC exam if not included yet (I don't remember I have ever seen it).

Il 17/lug/2018 15:19, "Jerry Gaffke via Groups.Io" <> ha scritto:
The receiver spec's how big of a signal goes in to give a desired result.
The microphone spec's how big of a signal goes out given a specific input sound level.
So the first gets a smaller number if more sensitive, the second increases if it's more sensitive.
Totally different industries, totally different notions of how to go about it.

A receiver's sensitivity figure in dBm tells us how much power must be coming in the antenna port
to achieve a specific result, in this case the "minimum discernible signal".
A power level zero dBm is arbitrarily defined as 1 milliwatt, and since typical signals at the receiver
are much lower in power, the receiver sensitivity is a fairly large negative number.

The microphone's sensitivity is defined as how big of a voltage signal we get coming out
when the microphone is presented with a sound pressure of one Pascal, and zero dBV is
arbitrarily defined as one Volt.  

Most of the speakers I buy state something like: "Response from 20 Hz to 20 kHz".
Not very precise.
They don't actually say what the response is, could be argued that catching fire is a response of some sort.

Here's a webpage on speaker sensitivity:

Sensitivity is most easily defined as the speakers’ ability to effectively convert power into sound. The traditional way of measuring a speakers’ sensitivity is using the standard of 1 watt/1 meter. Meaning a microphone is placed 1 meter away from the speaker to measure the sound output (in decibels) with 1 watt of sound played through it. "

So like the microphone, they spec how big of a signal goes out (sound in dB) when given a specific input (1 watt of electrical power).
Makes sense, as would have been the same engineers working with microphones and speakers back when these things were defined.

Next question: 
What is 0 dB of sound, and shouldn't that dB have a letter following it to tell us what the baseline is when finding that ratio?

Zero dB of sound is defined as the minimum discernible signal for the typical human ear.
No final letter because, well, it's a different group of engineers who defined it and they didn't care about the resulting confusion.


On Mon, Jul 16, 2018 at 11:50 PM, iz oos wrote:

Thanks Jerry, I had always thought the opposite, the lower the more sensitive just like sensitivity in a receiver. So, I was wrong. What about sensitivity in headphones and speakers?


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