A few years ago, I would have told you not to even consider ceiling mounted microphones. Although they have long been implemented, they tend to not work well. The reasons are simple. Uneven coverage and noise.
Uneven coverage happens because these mics will be varying distances from the different people speaking in the room, resulting in volume differences. Makes sense, right? I can hear someone next to me much better than another person five feet away.
Noise is pretty easy to understand also. If you put a microphone closer to the ductwork at the ceiling than the people speaking, you’re going to have a lot of ambient noise.
Digital processing has come a long way and we now have much improved tools to deal with these issues. Think of it like Bose noise cancelling headphones for your meeting space. So, does this mean we can just use ceiling mics? Well… not really.
When to go 1:1
Your results will never be as good as you can get with a 1:1 microphone ratio (one mic for every person). There are two times when you will immediately want to plan for the 1:1 scenario. The first is when you have poor acoustics as described above (typically in a large reflective room). The second is when delivery of the audio is critical. Some examples may include County Chambers, Courtrooms, Delegation Spaces, and large Collaboration Spaces. This could apply equally to a corporate meeting room. If the space is used at a high level, “Excuse me, could you repeat that,” will not be tolerated.
Even if you can’t do a microphone for every person, you will still obtain better results with much less effort using microphones laying on a conference table or similar surface. So when can you use microphones mounted from above? When acoustics are good and either budget or aesthetics forces you away from the concept of table microphones
Ceiling Microphone Folklore
Manufacturers and some vendors will tell you that ceiling arrays will outperform table microphones. Pure fiction. On the other hand, if you are in the scenario I noted above, where you are planning for a room with reasonably good acoustics and you are nudged in the direction of ceiling microphones either by budget or aesthetics, the Polycom Ceiling Microphone or a similar product may be your best alternative.
When are Ceiling Microphones a Good Alternative?
According to Polycom, the microphone accommodates a coverage up to three times larger than competitive unidirectional ceiling arrays. I have not performed a controlled comparison, so I can’t confirm this claim. Regardless, you can connect up to four ceiling microphone arrays to a single HDX9000 video system or SoundStructure C12 or C16, which provide AEC (automatic echo cancellation), noise reduction, and AGC (automatic gain control).
The microphone obtains its 360 degree coverage pattern by utilizing three cardioid elements. The factor of three times greater than the competition’s range is based on the claim that this design can handle a room up to 1,600 feet with four arrays.
While systems of this type, steer the pickup pattern down toward the participants speaking below (and away from the mechanical noise at the ceiling), they still place the pickup point closer to the source of the noise (HVAC ducts and mechanical noise at the ceiling). While the rejection characteristics of the microphone will help, inverse square law will still apply. In other words, if that microphone is closer to the source of noise and further from the speakers, no amount of electronic gadgetry will ever completely overcome the competitive advantage of a microphone placed close to a person speaking.
Yes, you’ll still hear papers shuffling and pencils tapping, but in my experience, these can be controlled to with proper gating to a greater extent than you can eliminate a constant source of noise, or just get a source closer to the mic element. Don’t get me wrong. Products like the Polycom Ceiling Microphone Array can be a great solution in a challenging situation. They just aren’t a panacea that should be relied upon for every design scenario.
Aren’t There Any Other Solutions?
So, you just read this entire article and at the end I tell you that you’re stuck between a rock and a hard place. Well, that’s not really true. I know marketing people love to tell you about magic bullets even when they don’t exist. Hopefully this article has already given you some insight to making the best decisions. I’d like to give you one more.
Instead of asking the question “What’s better – ceiling mics or table mics”, we instead accept the assumption that table mics are better but ugly. If this is true, then we should be instead focusing on how to make table mics less ugly. One company, Clock Audio, is doing just that.
The image below shows a conference table with small anodized aluminum microphones that pop-up out of the table. Fully extended, they are about an inch high. When recessed, they are nearly flush. The company offers microphones in nearly every conceivable shape, finish, and option… and their products are both beautiful and elegant.
In the arrangement shown above, the microphones are not one to one, but they still follow the basic rules of best practice regarding the distance from the person speaking. There are a huge number of options, including very slick LED light rings on the top of the microphone that can be programmed for various functions.
I know this is a long way from where we started, but hopefully this information will help you make some important decisions for your space design. While I mentioned the Polycom microphone at the beginning of the article, it’s just because I think they have the most advanced design.
With that said, several manufacturers will be coming out with similar products in the near future. This article is an examination of specific technologies, physics, and design approaches. Polycom still builds some of the best videoconferencing equipment in the world and it can be incorporated perfectly into a system like the one shown above.