February 2021

Audio Forecast
Over The Horizon
Some thoughts on the evolution of pro audio over the foreseeable future.
Article By Peter Mapp, PhD, FASA, FAES

  Predicting how audio-related developments will unfold over the next year is an almost impossible task, given the influence and effects of the current novel coronavirus (COVID-19) pandemic. As I write these words, the United Kingdom is in the middle of another lockdown; the same is the case for several other European countries. That was predictable, just as the second wave of COVID-19 infection was entirely predictable. What is not predictable, however, is exactly how all this will affect the pro-audio business over the next year or so. At present, there is a strange dichotomy: Some manufacturers, integrators and other firms are doing OK or are only down a few percentage points; by contrast, others are struggling to survive or, indeed, they didn't make it. My heart goes out to those in that position.

Clearly, businesses associated with remote-meeting software and hardware have done well, with the demand for their services and equipment having increased sharply. Moreover, microphone manufacturers have by and large done well — at the least, this category has helped to counteract the loss of business in the live-sound category.

Microphones
Obviously, sales of microphones and interfaces suitable for working from home skyrocketed, as did sales of higher-grade microphones for podcasts as this area took off and presenters came to realize the importance of broadcasting good-quality audio. (Never have so many Shure SM7B microphones been heard on air and over the ether! For a time, trying to get one was almost impossible, and they're still in short supply.) Now that most people in the world who wanted a separate or higher-grade microphone for their computer probably have one, demand will likely reduce and other markets will have to fill the vacuum. (Apparently, neither sound nor sales can travel through a vacuum....)

Beam-steering array microphones have also done well, having emerged as a maturing technology as more and more corporate meetings go online or become hybrid (i.e., some participants in the shared office/space, whereas others are at home or in their remote office location). The use of permanently installed beam-steering microphones has also escalated in the higher-education vertical; there, lectures and tutorials that are either completely online or a hybrid have become the norm. Accordingly, decision-makers have recognized the necessity of greatly improved audio quality and intelligibility.

Illustrations that demonstrate how sound can be localized and controlled using loudspeaker arrays and beamforming technology.

When ceiling- or wall-mounted beam-steering microphones are permanently installed, it means that microphones neither must be issued for a class nor passed around from hand to hand. These microphones aren't inexpensive, but, generally, they seem to work well; often, they incorporate ambient-noise-signal cancelling, something that simpler individual or distributed microphone broadcast and recording systems might not have.

What we need, however, is a standardized method for assessing these systems' sound quality and intelligibility. Simple speech transmission index (STI) measurements, for example, do not provide this. So, I hope that, over the next year or so, a practical and repeatable measurement technique/protocol is established. As a part of this assessment technique, the audio transmission and reception of the speech broadcast should also be rated, although that's outside the equipment manufacturer's control.

An interesting development within the microphone sector — one that I see growing over the next few years — is the use of microelectromechanical systems (MEMS) microphone elements for pro audio. MEMS have been around for a few years now, but, mainly, they've been used within specialist industrial areas such as test and measurement. They are effectively solid-state microphones, akin to capacitor transducers. Their small size, low output impedance and facility to incorporate on board digital circuitry make them ideal for use in high-electrical-noise environments. Semiconductor-fabrication technology and the inclusion of audio preamplifiers enable MEMS microphones to be manufactured with closely matched and stable temperature-performance characteristics. This is particularly beneficial for the manufacture of microphone arrays.

MEMS microphones are available in very small packages that are fully compatible with surface-mount assembly processes. Over the past few years, the units' audio performance has increased. Indeed, I'm aware of at least one cheap MEMS measurement microphone on the market, boasting a 20Hz to 20kHz +/-0.5dB performance, for around $75. I also noted with interest that, very recently, Shure released its first MEMS microphone. This 5mm boom mic is essentially dust-proof and waterproof, having an IP57 rating. Although the microphone isn't as sensitive as, and is slightly noisier than, its electret counterpart, the aberrations are small when compared to the benefit of having a microphone that you can dunk in water without any worries. That's an interesting ability when it comes to hygienic cleaning in this current time — and that's not to mention the host of applications that an IP57 rating might open up.

Speaker Developments
I have not seen, nor do I really expect to see, a corresponding step change in loudspeaker technology, although there has been increased performance and interest in micro-loudspeakers. An older "new" loudspeaker technology that deserves more interest is that of the Balanced Mode Radiator (BMR). Although it was invented around 20 years ago, it t'icle recasts one of audio's best-hidden secrets. Essentially, a BMR has wider controlled dispersion, which means that one driver can cover the midrange and high frequencies without the need for a crossover. BMRs can radiate well into the ultrasonic region, which, by itself, presents some interesting communication applications these days. An added advantage is that BMR-based loudspeakers can have the same dispersion characteristics in the vertical and horizontal planes, as there is no second driver and X-over to screw up the radiation.

An interesting application of BMRs could be off-the-ear headphones — a technology that I, certainly, would be interested to see develop. By locating the driver a little away from the ear, some interesting spatial-audio effects can be realized. What's more, it avoids the potential fatigue of an ear pad pressing down either on or around the ear.

I expect to see improvements and advancements in subwoofers. One area of advancement will be from a control point of view — for example, passive cardioid subwoofers that don't require complex digital signal processing (DSP) and multiple amplifier circuits to set up. Moreover, I believe there's a capacity to improve subwoofer phase performance.

Headsets
On the topic of headphones, I find it interesting how increasing numbers of manufacturers are entering this market. For some companies that have a basis in microphone technology, this is a logical extension and diversification; after all, dealing with small mechanical components and their micro-acoustic environment is second nature for them. For example, a long-established microphone manufacturer, Audix, is a newcomer to the headphone sector, but the company has been making in-ear monitors (IEMs) for quite a while.

Speaking of IEMs, they represent an area that is due for some attention. Just as with headphones, there is no standard frequency-response curve for IEMs; however, unlike headphones, there appears to be little to no published research as to what it should be. Every manufacturer has its own take on that. As such, it's quite possible for a monitor engineer to have to contend with two or three different responses. How does one get stable sound quality when band members could each be hearing something different? And who knows the actual levels to which the users are listening. Indeed, do we even know if the IEMs are working correctly and being reasonably consistent between the left and right ears?

Although IEM manufacturers might well have — indeed, should have — calibrated acoustic couplers/artificial ears to develop and test their products, these are prohibitively expensive laboratory instruments and aren't suitable for field use. I have seen some developers/test-and-measurement gurus actually 3D print their own "ears" and couplers, but what's really required here is an affordable test-coupler unit that was developed for field use. That could be a game changer. It would enable a more uniform frequency response to be provided across band members' IEMs; moreover, by calibrating the levels, the actual sound pressure levels (SPLs) being delivered to the talents' ears could be monitored.

While researching this piece, I discovered that such a device might soon be on the market. I can't really say whose product, but watch out next year for the TM2 if this area interests you!

While I'm on the subject of instrumentation, which, these days, is usually an audio computer interface driven by specialist measurement software, I hope to see more psychoacoustic-based measurement software introduced. Yes, measuring a standard frequency response is certainly useful; however, when it comes to subjectively assessing frequency balance, noise and distortion (to name just a few parameters), all of them have to be related back to a psychoacoustic reference. The measuring instrument /software should do this automatically for us. This could find immediate use in the assessment of voice-over-IP (VoIP) systems, for example.

Networked Audio
Speaking of audio over the internet, that area will certainly continue to expand over both the short-term and the long-term future. Here, I don't just mean videoconferencing, but, in addition, the transport of audio data around an installation. Networked audio is here to stay, and it opens up considerable flexibility, new opportunities and perhaps even cost savings. In particular, if the integrator can dial into the system and check for faults before he or she departs to the site, it can be very helpful and quite timesaving. In addition, the integrator, working from his or her office or home, being able to make changes to, or perhaps reconfigure, the system for a particular event is a value-add and a chargeable service. Although this has been possible for many years, I now see it trickling down to smaller projects and facilities (although, one would hope, there's also an upgrade in access security).

Power Over Ethernet
An associated area that's due for growth centers on the development of networked active loudspeakers and, in particular, Power-over-Ethernet (PoE) loudspeakers that connect directly to the network and that are powered from the network itself. This format can offer a very flexible approach in which individual speakers, or groups of speakers, can be paged as required and the groupings reconfigured at will, all without having to rewire. A single Cat5 or Cat6 cable to each speaker is all that is required, as the cable carries the digital signal, control, information and power. I can see the usefulness of the PoE approach for basic paging systems (i.e., not life-safety ones), although, admittedly, the power budget and the maximum transmission distance of 328 feet (unless both are boosted) can be a limitation.

At present, the PoE approach's insurmountable problem (as far as I'm concerned, at least) is the fact that it doesn't meet European life-safety standards. Unfortunately, there's no "quick-fix" solution to this. It's worth noting that every paging/voice-announcement system that I've designed over the past 10 years is also — indeed, is primarily — a life-safety system; as such, it must meet the associated stringent codes and standards. I also design multiple sound-reinforcement systems every year, but, at this point, I see no advantage in going the PoE route for these. As the power ratings improve, that might change; however, at present, the power available falls well short of my requirements. Nevertheless, POE is a technology of which to be aware and to bear in mind when one can exploit its benefits — in particular, in IT-centric installations, such as conference rooms and the like, in which wiring everything in familiar Cat5/Cat6 cables could be advantageous, while also potentially allowing for improved control.

Beam Steering
A loudspeaker technology that has the capability for further expansion and greater exploitation is beam steering. Although the technology has been around for well over a decade, there is scope for a trickle down to less-complex and less-expensive formats, and even for passive steering to be better developed. Although, here, I am primarily thinking of speech-based systems, the trickle down can apply just as much to full-range and music systems. By controlling the emitted sound so as to minimize reflections and reverberant excitation, it is possible to optimize speech clarity and intelligibility.

At present, most steered arrays are reasonably expensive; thus, a potentially large market for less-costly systems is being missed. Equally, the setting up of the current range of line arrays could be vastly improved and simplified, if not altogether automated. This process needn't be highly complex, but it could be one in which an artificial intelligence (AI) approach could reap rewards. Indeed, the use of AI to set up and optimize sound systems in general could be a fruitful area for future development.

An illustration that shows what's possible with the latest advancements in sound control and immersive/positional audio.

Although I've generally tended to use steered arrays to minimize reverberant excitation, there are numerous reasons to steer sound in spaces that are well controlled (i.e., non-reverberant), as well. Having the ability to put sound just where you want it — and effectively nowhere else — has many applications; they range from museum exhibits to home-entertainment systems in which different people can enjoy different program material/audio content simultaneously, without mutual interference. Car-audio manufacturers are also actively investigating this idea. Indeed, it's even possible to beam sound to an individual's ears and provide that person, individually, with immersive (spatial) audio. The idea of locating sound to a specific point (or a series of locations) can be exploited in large venues, as well, by using, for example, Wave Field Synthesis techniques.

Although simple mono, or even stereo, sound-reinforcement systems in a theater serve a purpose, they're effectively outdated these days. Arrays of loudspeakers located both across the stage (five sets, for example) and around the auditorium enable audio object tracking and permit a considerably more immersive audio experience. This is already becoming relatively common, with several manufacturers creating hardware and control software to do this. However, the capacity to steer sound beams both vertically and horizontally simultaneously opens up a whole new range of possibilities, and it enables audio objects to be more accurately virtually located. In addition, potentially, the ability to control sound in three dimensions enables one to obtain even greater clarity and intelligibility.

Adaptation
Although it is interesting to look out to the technological future, many developments can only take place if organizations can afford to fund them. That's a debatable question in these uncertain times. However, there are still clients out there with capital to spend. Serving them might require adopting a different business model or changing the range of products or services being provided; however, undoubtedly, those firms agile enough to respond and adapt will survive.

Some pro-audio manufacturers are taking a turn toward domestic markets, whereas others are just adapting what they do. A good example is a startup company that was all set to debut its AI-based immersive sports mixing system the week the first lockdown hit in the UK; this, in effect, killed off the company's novel product. However, some quick thinking enabled the company to adapt what it was offering and, thus, provide realistic and synchronized crowd-reaction audio for games being played in empty stadiums. Indeed, the company's virtual-crowd-sounds adaptation was so successful, generating more than two million views in fewer than 24 hours, that it's now provided to several different facilities and over three different sports and leagues.

Although, in the short term, some in the audio business might be in for an ongoing rough ride, the future is looking encouraging, novel, interesting and, undoubtedly, increasingly digital.

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