AudioSharp

Music, Programming, and other topics related to the modern Music Engineering Scene.

Digital Microphones

Microphones are analog by nature. The membrane physically interacts with the airwaves around it, recording any vibrations is senses. So how in the world do you make a digital microphone? These were my thoughts exactly as I entered the workshop on the development of these mics.

What the heck is a digital microphone?
Before going too far into how digital microphones work, let's look at the regular analog flow of things.
Signal goes from the microphone to a preamp through an XLR cable. From there, it goes through an analog to digital converter, then routed to the mixing board or whatever interface you're using for your computer. This is all well and good, except it could be better.

Microphones have a Signal to Noise Ratio (SNR) of about 138dB. 24 bit recordings can handle SNR of over 140dB. The preamp, however, has a SNR of around 100dB. You lose 40dB of dynamic range because of this external preamp setup. How do you get around this problem? Digital microphones propose the solution.

Digital microphones combine these three components into one. The microphone has an on-board preamp and A/D converter, giving you a digital signal out instead of the analog signal. It uses special quantizing processes to get the full dynamic range of the microphone and eliminate the 100dB limit of usual preamps. The actual methods are a little too technical for this post - I may come back and dedicate a post to that process.

Great, so now I have to buy an entirely new mic collection?
Not so fast, there. The spec for digital microphones (AES42, I think)
is still being developed. Even after it's finalized, there's no reason to replace mics that sound killer. Digital mics are meant to augment what's currently available, not completely replace it.

What problems can I expect?
Ideally, none. Digital mics should be ready to go. Unfortunately, any experienced audio engineer can tell you that with digital signals comes a headache of problems. What about sample rates? Who controls the mic's sample rate? What sort of interfaces will be needed for these signals? These are all problems that are being worked out.

There are currently 2 modes of operation for digital mics. Mode 1 specifies that the microphone is its own master. It only operates at the sample rate that it is made for, and that's that. Mode 2 requires a separate interface to dictate what sample rate the mic should operate at. Even with these distinctions, however, different companies still have slightly different ways of doing things - meaning lots of hardware won't interact well with other hardware. This will hopefully become more standardized as AES42 is developed.

That's the brief overview. As I mentioned earlier, I may come back to fill in details on some of these things in later posts. If you can't wait that long (or for more detailed information), look up the spec at
www.hauptmikrofon.de/aes42/.

AES Conference Updates

My apologies for the nine month hiatus. School has been keeping me busy. I'll try to post some cool interesting things over the next month, starting with crazy stuff from AES.

Too much went on during AES to list it all in one post. For those who have never been to the AES conference, it's basically a gathering of all the people who matter in the audio industry. The biggest names in microphones, software developers, hardware, and anyone else you can think of gather for four days of sheer madness. Lots of workshops, technical presentations, and an auditorium full of companies showing off their latest and greatest products. It's definitely something worth going to at least once in your life.

Some things that struck my fancy:

  • Pro Tools 9 is out. Finally, hardware freedom (sort of) and automatic delay compensation
  • The new MBoxes look killer. Complete with aluminum cases and onboard DSP. No more routing a microphone through an aux bus before an audio track so you can compress vocals.
  • Izotope. New plugins. 'nuff said.
  • Digital Microphones
  • Wave Field Synthesis
  • Consumer Audio Format Debates
  • Lots more!
Some of these will get individual posts, and some other topics that I haven't mentioned will get some posts. These are just the biggest ones that stick out in my mind.

To everyone who was at AES - what did you think? What were your favorite parts? What would you like to see more information about?

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Chemzoar does not intend to provide complete walkthroughs of everything covered on this website. Before undertaking any projects proposed by this website, be sure to do your own research on top of what's listed here. Chemzoar does not take any responsibility for decisions made based on the content of this site.