Sound card / microphone impedance mismatch

Question

First of all I'm not completely sure this is impedance mismatch, but from what I found on the Internet I believe it is. It seems to be a common problem. The question is not as much about solving the problem as about why it is happening (if I'm right about the cause of the problem, of course).

I had this quiet microphone problem with several built in cards and microphones and now with a Creative Audigy SE. There's a microphone boost option which introduces a lot of noise with volume increase, but even this doesn't seem to give loud enough sound in some cases.

The mic on my current headphones is very quiet with Audigy SE without the boost but is very loud and low noise with an external Sound Blaster Connect.

So the question is have I just been unlucky with my sound cards and microphones or is it a common problem? And if it is a common problem why is it so difficult for the vendors to standardize on the sound card / microphone impedance?

Edit: the OS is Windows (XP/7), but I don't believe it is OS-specific.

Answer 1

Impedance matching is not used for microphones.

The microphone's output impedance should be much smaller than the sound card's input impedance, not the same.

More likely, your microphone's level is just too low for a sound card's line input.

Answer 2

I had a similar problem with a Mac mini. It turned out the sound card didn't have a preamp on the line-in (if I recall correctly). I ended up using a preamp (i.e., a piece of hardware linked between the microphone and the computer) from a friend as a workaround.

Answer 3

Most consumer grade computer audio gear is really bad. Creative, in particular, has a terrible reputation for sound quality. If the mic / soundcard combo is capable of reproducing understandable speech, consider yourself lucky. This is a common problem, especially with integrated mic / headsets.

It is not hard to standardize on impedance, but it is more expensive to maintain the quality control needed to meet that standard. Consumers have spoken with their dollars. Unfortunately, whatever they said is unintelligible, because they don't care about sound quality nearly as much as price.

Answer 4

The microphone boost driver option only boosts the levels digitally. Most analog-to-digital-converters in consumer hardware are pretty low quality and introduce a lot of noise if the signal levels are low.
Hence, you have to amplify the analog input signal before it reaches the soundcard. You'd usually use a microphone pre-amp or a more sophisticated soundcard for that.

However, what is it exactly that you want to do with the microphone? If you are using a headphone mic, it is meant to be positioned very near the mouth and will not be any good anywhere else. If you want to record more than one persons speech, you could use a simple USB-mic instead since those include pre-amplification.
Also, as Benjamin pointed out you should never connect your microphone to a line-in. Use either a mic-in or a pre-amp.