Bluetooth and Auracast are changing the way microphones are designed

Most people have a view about their speakers, earbuds and headphones. They’ll happily enthuse about the audio performance, how well the noise cancellation works, their battery life and features like transparency. But nobody talks about microphones. The most you’re ever likely to hear is an exasperated “can you hear me” during a phone conversation, or a possibly muted oath about whether they’re muted and how to turn the mute on or off.

A large part of the reason for that is that speakers, earbuds and headphones, like the amplifiers and phones behind them, are almost exclusively sold on the perceived quality of the sound they produce. They’re designed to make money for the recording industry, who want us to appreciate the content they sell us (or increasingly, hire to us via streaming services), in the hope that we will consume more of it. They regularly offer us improved codecs, frequency responses which would challenge a bat’s hearing, and cutting edge reproduction through dynamically balanced armatures. Nobody outside the industry really understands any of that; few customers can appreciate it, but on the whole, we’ve been well trained to believe whatever new jargon is thrust upon us and fall into the trap of constant cycles of upgrades.

What nobody talks about is microphones, which have been the very poor cousin of audio reproduction, at least in consumer products. That’s partly because personal microphones make no money for the recording industry. Their business model doesn’t encompass users generating their own content, as that reduces the time their users have available for buying and listening to more pre-recorded content. The other reason is that until recently the microphones in phones and earbuds have only been used for phone calls, and if your voice isn’t very audible, everyone blames the phone and the mobile network. That gives manufacturers very little incentive to invest in designing better microphones.

In the past few years, two things have started to change that. Firstly, mobile networks and phones have finally got around to upgrading the quality of the audio they support. More importantly, TikTok and its imitators have started a revolution in personal content generation. Both have highlighted the limitations of current wireless solutions for microphones. Fortunately, the arrival of the latest Bluetooth Low Energy Audio technology is about to revolutionise the way that wireless microphones are designed, elevating them to support high quality, personal content generation.

Designing a better TikTok microphone

Whatever people may think about TikTok, it has democratised content generation in a way that nobody expected. Unlike YouTube and other predecessors, you need no technical knowledge to record and post a video. You just start an app and point your phone at something, which is normally yourself. It’s no surprise that it came out of China, as it’s a “mobile-first” application, where most users’ first internet experience is on a smartphone, not a PC. Its ease of use and popularity contradict the existing industry mantra that consumers want the slick production values of Hollywood.

TikTok took advantage of the capabilities of smartphones to make it possible to generate and share videos. Its original, limited recording length was a master stroke, as it meant that users didn’t need to spend time scripting or rehearsing their contributions, they just did it. The barriers for personal content generation disappeared, and the balance of content creation began to move into the hands, or rather the phones of the consumers.

Almost every smartphone today has a highly competent camera and easy to use content creation apps. The only bit that’s still missing is a decent microphone. But that’s about to change. Not in the phone, but with the advent of new, high quality TikTok microphones.

You may wonder why anyone would want a TikTok microphone, but using a separate microphone addresses a couple of flies in the TikTok video production ointment. One is that holding the phone at arm’s length doesn’t provide the most stable video, but that can easily be solved by a plethora of holders, clips and tripods. The more intransigent one is that phone microphones aren’t really designed for recording videos.

There are three problems with phone microphones if you’re using your phone to film videos. The first is that they’re generally designed for capturing voice, not music. (Which is about the only aspect of smartphone design where the phone functionality still wins out.) Latency – the time it takes from recording your voice to transmitting it onto the network is paramount, otherwise you start to add delays into every conversation. However, most traditional low latency codecs, which convert your voice into a digital stream, achieve that short latency by limiting the frequency response. That’s fine for a voice call, but it isn’t what you want for a quality video.

The second is that the microphones on phones don’t point in the right direction. Once again, phone requirements take precedence, so they’re optimised to pick up your voice during a phone call, which means that they’re typically pointing downwards, at right angles to the camera. That’s because phone design still assumes that most people hold their phone to their ear during a call, so the speaker output is at one end, and the microphone input at the other.

The final issue is a more practical one, which is that as the microphone is on the phone, it picks up all of the sound around it, not just your voice.

For those reasons, anyone wanting to improve their TikTok video quality quickly invests in a remote microphone to solve these problems. You can use earbuds, which help, but although they are designed for high quality music reproduction, manufacturers still assume that the microphones in them are only going to be used for phone conversations, so they have relatively low audio quality codecs.

There are plenty of remote wireless microphones already on the market to help TikTokkers, but they share most of the problems of earbuds. To implement high quality, low latency encoding is tricky, which is where the new Bluetooth Low Energy Audio standard comes in.

Bluetooth Low Energy Audio is a new specification that started with hearing aids, but rapidly expanded its remit to provide a new generation of high quality, low power audio capabilities. It’s rewritten the rule book about wireless audio. For the first time, we have a wireless standard which combines low latency with high quality in both directions. It also supports multiple peripheral devices at the same time. It has been designed so that you can stream to and from earbuds, hearing aids and speakers, keeping them in perfect synchronisation with each other.

For anyone wanting a better microphone, it offers everything you need. Once you have a phone which supports Bluetooth LE Audio, it can set up a connection to a handheld or body worn microphone that records you, without any extraneous audio pickup. The new LC3 codec captures high quality audio, and the overall latency between you speaking and the phone receiving the audio stream can be less than 30ms – far lower than any perceivable lipsynch issues.

Even better news is that the Bluetooth LE Audio topology supports more than one microphone being used at the same time, so your phone can work with independent microphones to record two or three participants in a podcast, or record your voice along with a separate microphone on the instrument you’re playing. Each of those audio inputs is synchronised to within a few microseconds (this is microseconds and not milliseconds), so that your audio tracks are perfectly aligned.

The technology ticks every box that a TikTok creator needs. Microphones should start to be available in the very near future. And if you have an older phone that doesn’t support Bluetooth LE Audio, you’ll be able to purchase a dongle to plug into its USB port to make it all work. It removes one of the last constraints of using your smartphone to capture high quality videos.

That’s not the only exciting new feature of Bluetooth LE Audio. As well as supporting better quality and lower latency audio, its Auracast feature lets you share audio.

Auracast and Sharing

You may not have heard of Auracast yet. It’s the flagship feature of the new Bluetooth Low Energy Audio specifications. Unlike any wireless consumer audio standard we’ve had before, Auracast is specifically designed for sharing audio, whether that’s voice or music. In terms of its impact, it’s probably the biggest real change that we’ve seen in audio since the introduction of stereo back in the late 1960s.

At its simplest, Auracast lets you set up a broadcast audio transmitter which anyone within range can listen to. It takes its origin from the telecoil loops which provide audio to hearing aids in public venues, but supports the high quality and low latency of Bluetooth LE Audio. It also allows multiple audio streams to be transmitted at the same time. In most cases, that will be separate left and right stereo streams, but they can be complemented by a mono stream, streams designed for listeners with hearing loss, or multiple streams in different language.

Auracast will transform the way we use audio, bringing social applications to the fore. It will also have a major impact on microphone design, as a Auracast transmitter can be integrated into a handheld microphone, providing a complete wireless audio solution. As the diagram below shows, a single Auracast microphone can broadcast to any number of headphones, hearing aids and earbuds within a venue, as well as being picked up by PA speakers. The new standard has also extended the range compared with classic Bluetooth audio, so that a single transmitter will cover most venues.

Every receiving device in the room will render the audio at exactly the same time with minimal latency, so the listener with the single hearing aid will not notice any different between the ambient sound arriving in their left ear and the Auracast audio stream arriving in their right hearing aid.

Unlike telecoil, which is expensive to install and only available for hearing aid wearers, Auracast transmissions will be accessible to anyone wearing Auracast compliant earbuds or headphones. These are already appearing on the market.

Shared audio is going to be transformative. Many will use it to share music from their phones or to listen to TVs, but using it with microphones will make so many applications so much easier. Whether its for conferences, meetings, silent discos, yoga classes, theatres or cinemas, we are about to see some radical changes in microphone design and the way we use sound. It’s time to listen to the future.

If you’re in the UK on 7th March you can learn more about Auracast at an afternoon seminar in Cambridge, hosted by Cambridge Wireless. Register for free at https://www.cambridgewireless.co.uk/events/auracast/, using the delegate code CDGUEST070324, which will apply a 100% discount.