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I want to create a microphone array that can be connected to my laptop. Previous discussions in stack exchange and other forums suggested me to get a USB audio interface. I would want to do a lot of real time signal processing on the sound arriving at the microphones (To be precise, I want to calculate the time delay of arrival of sound at the different microphones). But from what I saw, the audio interfaces are a bit expensive. But external sound cards are not! Here:

http://www.ebay.com/bhp/external-sound-card-for-laptop

Can I use an external sound card to receive input from multiple microphone (create an array, that is).

I will require 4 mics, but right now I need to do it with only 2 mics to test the algorithms. Sampling rate would be around 40Khz.

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  • $\begingroup$ Can you edit your question to add more details: What number of mikes, what sampling rate, what frequency ranges, .... This question is too broad as-is. $\endgroup$
    – Peter K. ♦
    Commented Nov 17, 2013 at 18:55
  • $\begingroup$ The question is too broad because I really didn't know how to trim it down. I have edited it as you requested. $\endgroup$
    – Kevin Martin Jose
    Commented Nov 18, 2013 at 6:48

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Sound card == audio interface

The only difference is that the name "audio interface" is usually used for pro audio equipment. On the other hand, "sound card" usually refers to consumer audio.

Currently there are no cheap multi-input audio interfaces. You may want to check out second hand market, but even there USB and 1394 interfaces are expensive.

The only cheap solution that comes to my mind is to use multiple stereo-input interfaces and synchronize theirs clocks using SPDIF. Then you can link them on Linux (in asoundrc) or Mac OS. I don't know if it's possible on Windows.

However, I have never tried synchronizing clocks using SPDIF myself.

Without synchronizing clocks you need to use resampling which is computationally expensive and can degrade quality. alsa_in and alsa_out tools for Linux/JACK can do this. But they're usable only if you don't need accurate timing as they don't do latency compensation.

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  • $\begingroup$ That means I can use a sound card to create a microphone array right? Does sound cards have multiple audio input channels? $\endgroup$
    – Kevin Martin Jose
    Commented Nov 6, 2013 at 9:33
  • $\begingroup$ @lonesword only the more expensive, professional ones, which usually aren't called soundcards but audio interfaces. Devices dedicated to regular consumers never have more than 2 input channels (at least I have never heard of such soundcard). $\endgroup$
    – adiblol
    Commented Nov 6, 2013 at 18:14
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You can get pretty good and cheap multi-channel audio interfaces from the home-recording industry. Check out websites like sweetwater.com, musiciansfriend.com, zzounds.com etc. (no endorsement or product placement implied). Many of those come with low-latency ASIO drivers and you can integrate them with audio recording and processing software like VST, ProTools etc.

One step up from there are semi-pro setups like RME (http://www.rme-audio.de/en_index.php) which have many different high quality interfaces and programming platforms. (again: not an endorsement).

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