# Tag Info

### What is the reason for using decibels to measure sound?

If the decibel represents a gain ratio, why do we use it in sound measurements? Let me correct you; the decibel represents a ratio, and when used to talk about amplifiers, it represents a gain ratio. ...
• 465k

### What is the reason for using decibels to measure sound?

If you're trying to measure what a human being hears, dB make more sense than some system such as SI unit Pascals. Each 10dB increase in sound level appears to be roughly twice as loud. Since dB are a ...
• 407k
Accepted

### What is the reason for using decibels to measure sound?

The other answers focus on the large range in pressure which corresponds to sound, and suggest that this is the reason we use a logarithmic measure. This isn't really right: it's true the range is ...
• 15k

### What is the reason for using decibels to measure sound?

What is the reason for using decibels to measure sound? The point to understand is that we do not measure sound level as decibel (I will use dB as the short form). Decibel as such is, as correctly ...
• 527
Accepted

### Do audio impedance mismatches cause reflection (ie, 8-Ohm output to 20kOhm input) ? Does it matter?

Are there reflections? Thanks to Oliver Heavyside - Yes. Do they matter in power amplifier / speaker connections- No. Calculate the wave length of a 20 kHz signal, and compare it to the typical ...
• 21.4k

### How can I record with this old fashioned mono microphone?

That's not a normal mic. That appears to be a magnetic coil pickup for a land-line phone handset. They don’t pick up sound directly. Instead, these are stuck onto the handset earpiece side, and pick ...
• 55k
Accepted

### How do you choose an audio isolation transformer for a microphone?

The transformer that you linked to is not an audio transformer. There are transformers designed specifically for use with microphones. Their datasheets should give you the information you need, often ...
• 25.1k
Accepted

### What type of cap would you use to block DC on a microphone-level audio line (unbalanced)?

You need to know the frequency range you want and input impedance. If this related to the radio of your previous question, then the following is true: The mic input has 8 VDC bias supply and the unit ...
• 159k

### What type of cap would you use to block DC on a microphone-level audio line (unbalanced)?

Film capacitors are not microphonic and do not vary their value with applied volts, in other words they are linear. Polystyrene capacitors are good and expensive but I have not needed to use them. ...
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### How can I make an adapter wiring for a TRRS microphone to TRS?

For TRRS CTIA: Sleeve = mic Ring = GND (for mic and speakers) Ring = (right speaker, not used for mic) Tip = (left speaker, not used for mic) For TRS mic only: Sleeve = GND Ring = (not connected or ...
• 159k

### What is the reason for using decibels to measure sound?

dB SPL is computed by first measuring the actual sound pressure (e.g. in pascals) and then taking the logarithm, so people do measure the pressure, it is how you get the dB value. Typically though a ...
• 17.6k
Accepted

### Measuring voltage from the aux cable signal

The wires from the headphone are insulated. The green and red stuff on the wires is a kind of lacquer. It insulates the wires to prevent short circuits. You can't really remove it mechanically. ...
• 72.5k

### What is the reason for using decibels to measure sound?

There are a few main reasons. Sound pressure spans so large range that it makes sense to use a logarithmic unit to begin with, like for many other things like Richter magnitude scale for earthquakes, ...
• 159k

### How do you choose an audio isolation transformer for a microphone?

Do a search for something like 'microphone transformer data' (without the quotes). A problem is that many of the products are decades old and no longer available. But going through the catalogs and ...
• 21.4k

### Why does 9.7Vrms == 27 Vpp? I thought it was 9.7/0.707 == 13.72!

For a sine wave $V_{RMS} = \frac{V_P}{\sqrt{2}}$ Vpp = Vp*2 Audio that isn't a sine wave will be a bit different.
• 407k
Accepted

### Why does 9.7Vrms == 27 Vpp? I thought it was 9.7/0.707 == 13.72!

For one thing, the formula you posted is wrong. Vrms of a sine wave cannot be higher than the amplitude. Here are some formulas: Vpp = 2 × sqrt(2) × Vrms. Vp = sqrt(2) × Vrms. Vpp = 2 × Vp. An example....
• 159k
1 vote
Accepted

### Coupling/decoupling power supplies: how?

Not sure what this "Hi-Z" adapter device is...Maybe point to a datasheet? But in general if you are worried about multiple DC power supplies in the same circuit not having the same ground, ...
• 335
1 vote
Accepted

### How can I record with this old fashioned mono microphone?

You are likely plugging it into a port intended for headsets, not a mic. You need an adapter which converts a headset port into a headphone port and a mic port. Or plug it into some device which can ...
• 159k
1 vote

### Do audio impedance mismatches cause reflection (ie, 8-Ohm output to 20kOhm input) ? Does it matter?

Suppose a voltage source is connected to a load via a transmission line: We have a source impedance, load impedance, and transmission line length and impedance. What matters is the length of the ...
• 79.5k
1 vote

### Do audio impedance mismatches cause reflection (ie, 8-Ohm output to 20kOhm input) ? Does it matter?

Yes, impedance matching does matter in audio systems, if the wires are long enough. That usually means long microphone cords. The effect with 100 ohm impedance wiring, driving a 6 ohm speaker, is ...
• 7,683
1 vote

### Do audio impedance mismatches cause reflection (ie, 8-Ohm output to 20kOhm input) ? Does it matter?

Yes in fact there can be reflections due to impedance mismatched in the audio system, just like in any other system, but due to low bandwidth as the frequencies are so low, you generally run into them ...
• 159k
1 vote
Accepted

### What is the maximum dBu I can send into a microphone input in this schematic?

The op-amp is powered from 5V and has rail-to-rail output, guaranteed to be 4Vpp. We can assume ideal 5Vpp for simplicity. It is an inverting configuration, with gain of 20.6, which means the op-amp ...
• 159k
1 vote

### What is the maximum dBu I can send into a microphone input in this schematic?

The circuit has external input overvoltage clipping diodes, but we need to see more of the schematic to evaluate them in this circuit. Here is something to consider . . . The opamp circuit is ...
• 21.4k
1 vote

### What is the reason for using decibels to measure sound?

Another distinction I haven't seen made between sounds and distances is that distances add linearly, but sound levels don't. If two devices that would produce sounds at a certain pressure level are ...
• 47k
1 vote

### What is the function of the inductor in this Bluetooth audio module?

It's meant for filtering the supply power, though I'm not convinced it's a good idea to use an inductor here. If you have a dirty supply, or if you need to keep noise from the bluetooth module out of ...
• 35.3k

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