Microphone Advancements

[Bleep314]

I am doing an assignment for college with regards to microphone advancements and what microphone designs and innovations might be around in the future. Can anyone on here recommend any articles or further reading that might give me an insight into microphone designs for the future? I read an article about digital microphones on the SOS website and are hoping for more of the same.

Thanks for your help,

D

[Hugh Robjohns]

An exploration of the AES journals might reveal some glimpses of some future mic technologies, but for real cutting-edge technologies I would suggest investigating optical mics (using laser interferometry), and the 'microflown' design which senses air currents directly through the cooling of a heated terminal. Optical mics are already in use in the oil and gas industry for sensing leaks in pipes and storage tanks without the spark risks of direct electrical connections. These are radically different technologies from what we have been using up to now.

On a more pragmatic here-and-now level, I would also look at DPA's phenomenal development of sub-miniature and small-diaphragm electret capsules, and AKG's unique development of large-diaphragm and multi-pattern electret capsules. Electret capsule technology has improved massively over the last 25 years.

And then there's Sennhesier's unique development of symmetrical capacitor capsules (in the MKH range) which have astonishingly low THD, and Neumann's pioneering work in developing digital capsules with very clever integrated A-D conversion... And maybe the square and triangular capacitor capsule designs of several of the smaller Nordic mic makers...

There's also the work by Audio Technica in its discontinued AT895 and Schoeps (with its super CMIT) in the use of DSP to process the outputs of multiple capsules within a single mic body to improve microphone directivity (in particular as applied to shot-gun or rifle mics), and of the (discontinued) Trinnov SRP surround-sound mic array ( http://www.trinnov.com/wp-content/uploads/downloads/SRP_EN_A... )

And in the dynamic realm, Shure's recent development of a dual-diaphragm moving-coil capsule, and the improvements in ribbon diaphragm materials and magnets, especially by Rowley and Trip (now marketed as Shure mics). Graphene-based diaphragm materials hold out much promise too...

Many of these mics and research areas aren't new as such, but are certainly still on-going and will continue to evolve in the future.

Hope that helps...

[SimonZ]

While they're not (yet) part of the studio world, you should include MEMS microphones as a new(ish) technology.

[Hugh Robjohns]

Yes -- very good call. It's yet another example of how mobile phone technology is impacting on the pro-audio world.

For anyone that's not heard of 'MEMS microphones', MEMS is short for 'micro electro mechanical systems' and it's basically a technology that allows miniature electro-mechanical systems to be constructed and implemented on silicon wafers much like conventional integrated circuits. A related technology is used for measuring gas flows like the MicroFlown system I mentioned before.

MEMS mics are basically sub-miniature DC capacitor mics built into an IC, and although there are analogue versions, most now are designed as digital mics, converting the changing acoustic air pressure into an oversampled pulse-density signal running at around 3-5MHz, and then converting that into conventional PCM for the rest of the signal processing system in the phone or whatever.

Early designs struggled to get a response below 100Hz but the latest versions claim to manage a 20Hz-20kHz range with reasonable noise and distortion -- at least in the context of a mobile phone's requirements. The cost is now directly comparable to traditional electret mics, but they are much more compact and can be made to provide digital outputs as I said, so they are more convenient in many cases.

As Simon says, the technology will continue to improve and evolve and open a range or new applications (especially in directional steerable arrays for surround sound and other applications).

H

[The Korff]

...then there's light- and laser-based mics (the latter of which are used for surveillance rather than music, but still interesting).

Cheers!

Chris

[SimonZ]

Unfortunately the focus for MEMS mic development is on smaller and cheaper rather than bigger and better.
Since they are good enough already for phones.
I was at a MEMS facility not long ago and had an interesting chat with some device guys about could you make a really good quality MEMS mic.
The answer was that you probably could make a very good one but the market is far too small to bother.
Those guys have to make and sell things by the million to make money.
Unless there turns out to be a military application ..... then it might get done

[Hugh Robjohns]

The answer was that you probably could make a very good one but the market is far too small to bother. Those guys have to make and sell things by the million to make money.

Yes, too small, and too quirky -- it would be a major uphill struggle to persuade the GS market that a MEMS capsule offered any sound advantages over their vintage U47 ...or a modern 'clone'

H

[SimonZ]

With you there Hugh !
I can imagine uses for a mic that starts omni and then you use an app to draw in the response however you wish.
Oooh, today I need a clover leaf pattern, turn down the floor reflections a bit and turn up the ceiling reflections a bit.... done !

[Hugh Robjohns]

With you there Hugh !
I can imagine uses for a mic that starts omni and then you use an app to draw in the response however you wish.
Oooh, today I need a clover leaf pattern, turn down the floor reflections a bit and turn up the ceiling reflections a bit.... done !

I'll buy a matched pair!

[John Willett]

There is also the optical coupling of phantom power that totally electrically decouples the power from the audio chain, as used by Microtech Gefell in several of their mics.

There is the ceramic capsule that makes a more stable capsule as it does not expand and contract like a metal capsule and keeps the diaphragm in a constant tension.

There is also the optical mic.

I have also heard about research into using graphene as a microphone diaphragm.

If you want to read more on DIgital microphones, then my AES papers on the subject are HERE.

There is an article about Digital microphones being used at Abby Road HERE.

The artical about using digital mics for a piano recording in the Menuhin Hall is HERE.

The forum thread on the Neumann KM-D digital mic. is HERE.

There is my AES paper on Sennheiser's symmetrical capsule HERE.

My article about the RF condenser mic. is HERE.

I hope this helps.

[Bleep314]

Thank you all for helping me with this. The replies I have had were all really helpful and made for excellent reading. All suggestions made were enlightening and has really opened my eyes to new possabilities.

Again, thank you to everyone who replied. I really appreciate it.

D

[Hugh Robjohns]