Electrical – Voltage of sounds of MP3 files

soundvoltage

What is the maximum voltage for common music files?

When playing back on a smartphone, if the volume of the smartphone is set to maximum, how much voltage is sent to the earphones of the electric signal?

thanks so much for comment
I’m japanese.
I’m not good at English.
I use google translator.
I want to use a low frequency therapy device on my smartphone. I thought it was dangerous depending on the voltage. And I asked this question. any precautions or dangers?

Best Answer

Amplification

It does not depend on the music file, but at the amplifier sending the music to a speaker, or to a headphone/earplug connector.

Music file

A music file only contains 'values', and mostly in a compressed form. After uncompressing, you get values which has a certain amount on bits per value (typically 16 or more).

Conversion

A microcontroller can send these values to a speaker via an pre- and/or amplifier, which converts it into actual voltages. So it depends on the amount of amplification.

Protection

Also note that sending continuous 'max values' do not result in a loud sound, actually it would breaks the speaker (to prevent this, in the amplifier a so-called DC speaker protection is present). A wave is needed to let the speaker move outwards and inwards very fast, and this is done by sending changing values to the speaker.

Measure

If you want to measure, you can use an oscilloscope to measure the audio output while sending a sine wave with a maximum amplitude.

Related Solutions

Electronic – Polyphonic sounds from a microcontroller

Well one easy trick is to use two pins with PWM, and tie them to the opposite sides of the speaker. Then modulate each pin at a different speed, and you can play two notes at once...basically the speaker is mixing them together for you. More than two notes and you will have to do it in software as mentioned.

Electronic – arduino – How to output sounds over a headphone wire

The easiest way to make noise is to rapidly turn an output on and off.

The faster you turn it on and off the higher pitched the sound will be.

One common way of doing it is to use one of the PWM outputs, which gets turned on and off for you by the chip.

If you want to get more fancy you can look into how you can emulate a Digital to Analog converter using PWM, or read up on creating an "R/2R" resistor ladder DAC. That would allow you to create more complex waveforms.

Edit: I wrote this before I had used an Arduino much.

It's very easy on an Arduino.

Connect a speaker / headphones / piezo sounder between one of the PWM pins (marked with a ~) and ground.*
In your sketch call the tone function: tone(pin,frequency[,duration]);

(Frequency is in hertz, and duration is in milliseconds)

For example, if the speaker is on pin 6 then you can use:

tone(6,440,1000);

Which will play A4 for 1000ms (1 second).

*: Because the tone you are playing is an AC signal, good circuit design would dictate that you place a capacitor in line with power to couple your signal. However, you're using headphones here so it doesn't really matter too much; the effects become more significant when you're driving a larger load (e.g. a speaker).

Best Answer

Related Solutions

Electronic – Polyphonic sounds from a microcontroller

Electronic – arduino – How to output sounds over a headphone wire

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