Auracast™ Audio. Better than the original?
- Published
- in Hearables
If you’ve not heard of Auracast™, it’s time to find out about it. It’s part of the new Bluetooth Low Energy Audio specifications which support broadcast audio. What that means is that it allows individuals and places to share an audio stream, so that multiple people can listen to the same thing.
Auracast builds on the telecoil experience, which has been part of hearing aids for many years, but supports a new codec, called LC3. This can be used to generate high quality audio with such a low latency that the Bluetooth stream can reach your ears at the same time as the ambient stream. Last week, Auracast had its first major public demonstration in the US at a performance of Richard Einhorn’s “Voice of Light” in the Lincoln Centre in New York. A number of users, both with and without hearing loss were able to hear how it works. I was one of the lucky few to try it. Talking to others after the performance, it was obvious that not only did it work exceedingly well, but the audio quality was so good that we were starting to have some fundamental questions about how live music is recorded. Andrew Bellavia has already written about the devices which were used. I was fascinated with the resulting experience.
First a few words about the concert. Richard wrote “Voices of Light” to accompany the “Passion of Joan” – an amazing silent film made in 1927, based on the transcripts of the trial of Joan of Arc. This performance had an orchestra of around 60, with a choir of 120. It’s a magnificent piece and it sounded amazing in the 1,000 seat auditorium. The venue was recording the performance for archival purposes, using multiple microphones for the orchestra, the choir, four soloists and six sopranos singing the role of Joan, who were positioned on a balcony above the left side of the auditorium. These inputs were mixed to generate a stereo output, which was fed to an Auracast transmitter supplied by GN Resound – the hearing aid company that enabled this demonstration. That transmitted a stereo Auracast stream to a couple of dozen users who were spread around the auditorium, wearing GN’s latest hearing aids. Around half of us did not have hearing loss, so these hearing aids were set to provide minimal additional amplification.
The performance was not amplified. The venue – the Alice Tully Hall is a concert hall with great acoustics. That meant that we had the choice to listen to the Auracast feed or the ambient sound. Because of the low latency of the Auracast system, there was no perceptible echo, even if you mixed the Auracast transmission with the live ambient sound, which was possible with GN’s Nexia hearing aid app. That is where things got interesting.
The sound quality was amazing. What was more interesting was the discussion afterwards, which quickly moved from a technical discussion about the Auracast performance to a debate about whether the ambient or Auracast stream was better. “Better” is subjective, but most people I spoke to preferred the Auracast stream, which came from the mixing desk. They felt it was clearer, and that the stereo separation enhanced the solo voices and particularly those of the singers portraying Joan at the side of the hall. Others (Andrew was one), preferred a mix of the ambient and the Auracast signal.
By coincidence I’d just finished reading “The Emperor’s Soul” – a short novella by Brandon Sanderson (which I thoroughly recommend), which takes as its theme the question of whether a forgery can be better than the original. It felt that most of those listening to the Auracast stream felt that way about the concert. What is interesting is that the Auracast stream coming from the mixer is what you would hear if it were released as a “live” recording of the concert, which is different to what most of the audience would have heard. That’s nothing to do with Auracast, but it’s a distinction that I don’t think any of us would have made before, because we’d not have been able to switch between the two simply by adjusting the mix in the app.
There’s a lot spoken about audio quality, but very little about audio authenticity. Being present at the concert where we could experience it was fascinating. It wouldn’t have been possible if the Auracast stream hadn’t been so good – both in quality and latency it sounded perfect. It’s great credit to the LC3 codec and GN’s hardware that it delivered that level of performance. It was so good, we could compare the difference between the acoustics of the hall, and the multi-microphone mastering of the recording engineer.
The other excellent piece of news is that all of this was done with products that are currently available. The Auracast transmitter was a “TV streamer” from GN Resound. It’s a consumer device designed to plug into the back of a TV to help hearing aid wearers. All that was required was to plug it into the output of the mixing desk and attach it the ceiling of the auditorium.
The concert was an excellent demonstration of Auracast’s capabilities and a wake-up call to everyone to say that the technology is here. I’d expected it to be good, but I hadn’t realised that it would be this good. It was a clear demonstration of the fact that Auracast is for everyone, not just people with hearing loss, as well as the fact that there are going to be unexpected applications that we’d not thought about. I’m looking forward to experiencing more opportunities to hear it.