Electronic – using headphones as microphone

headphonesmicrophoneoperational-amplifier

I am learning about headphones and microphones and I have 2 questions.

I bought a few pairs of headphones from the dollar store and took one pair apart. There is a weak little magnet in the center with very thin insulated wire coiled around it and there is a very delicate plastic sheet covering this little assembly. Now, the headphones worked before I took them apart so it's very exciting to see the guts. I've also studied this design and I think I understand the physics of it.

My questions are:

  1. Should I be able to use these kinds of headphones as microphones? I've thus far been unsuccessful.

  2. The headphone jack is tip-ring-sleeve. If I connect sleeve (which I think is common ground) to either tip or ring (and thus completing the circuit), can I use my multimeter to measure the current/voltage if I yell into the headphone?

My goal is to see (detect) this thing at work. I've learned a bit about op-amps too, and I wonder if I cannot do what I want without making a slightly more advanced circuit.

Kindly,

Best Answer

In most cases, headphone transducers will also work as dynamic microphone transducers. However, they put out a VERY SMALL amount of signal which you will never see on a regular meter. No it cannot be "amplified" by simply applying a DC voltage (from a battery or whatever). You need a high-gain AC amplifier. Specifically a microphone preamp to bring a "mic-level" signal level up to "line-level" which can be seen on a meter. Typically 40dB (10,000 x) of gain. There are hundreds of examples of mic preamp circuits online.

Most small microphone capsules used with computers, etc. these days are electret condenser microphones which are quite different than dynamic microphones.