Auracast as a promising technology for the silent discos and similar events
Article – From the horse’s mouth
Bluetooth
My Comments
There is a significant trend towards “silent discos” and similar “silent” entertainment events where participants wear supplied headphones to hear the audio content for the event.
The headphone-based silent disco
Such events take place in areas or situations where the playing of loud music is not really tolerated, such as to host the events past noise curfews or to host the events in a railway station, museums or similar places where loud music seems out of place. There are even people who run silent disco tours where the music is from a portable device but fed through a silent-disco setup and the participants follow the leader, dancing to the beat.
The current technology is based on 800-900MHz UHF analogue radio technology which can support the concurrent operation of three audio channels of stereo content. This would allow three performers to play in one of these events with the user operating a selector switch on their headphones to choose whichever performer they want to hear.
But these events require the hosts to acquire transmitter and headset kits and supply the headsets to the guests who want to participate. I even posed a question about Bluetooth Classic and its possibility in this use case but that technology is fraught with issues like latency which can impact dancing or following movie soundtracks.
Similar approaches that allowed users to use their own equipment
Another similar arrangement that has operated for a long time was to use a low-powered AM or FM transmitter in the classic drive-in cinemas to transmit the movie soundtrack through the car radios installed in the audience’s cars. Here, when the audience members arrived at the drive-in, they tuned their car radio or a portable radio to a particular frequency to hear the film’s soundtrack. This was in lieu of the wired speakers that used to be clipped to the car sun-visors which was initially the way to get the soundtrack to the cars.
It was even possible for this to work for those drive-in cinemas that ran up to three or four screens where they could show multiple films concurrently. This was facilitated with a transmitter for each screen and the audience tuned in to the relevant frequency for the screen they were viewing.
The use of low-powered AM or FM transmitters at the drive-in cinemas was effectively a “BYO equipment” approach to distributing sound that accompanied an entertainment over a small area. This was thanks to having the viewers use their car or portable radios to hear the soundtrack.
Similarly it extended to street activations, parades, fireworks displays and similar events that local radio stations ran or participated in during the 1980s and 1990s. Here, the participating radio stations broadcasted the music for that activity such as a synchronised soundtrack for a fireworks display or the dance music for a “dance in the streets” activation.
Participants brought their portable radios along or showed up in their cars and they tuned their radios to the station to hear the event soundtrack. Promotional material leading up to the event would contain a line like “Bring your ghetto blaster or Walkman and tune in to enjoy the event”. In some cases with streets that had retailers like cafes or take-out food shops that traded through the event, these retailers would tune their radios to the participating station so as to be in on the action. Some events that had a stage may have operated a PA system at the stage with the participant-supplied audio equipment being about extending the sound beyond the stage area such as along the street.
These kinds of events flourished thanks to the popularity of decent car, portable and personal audio equipment that was developed through the late 1970s and the 1980s and people wanting to get the most out of this equipment.
This scenario allowed the soundtrack for the event to be extended across the radio station’s broadcast area which can be a bonus for some events like fireworks displays that have wider areas of relevance. But it may not work well for events that have a focused area of relevance.
The drive-in cinema with its low-power radio transmitter and the local radio station that is involved in and providing the music soundtrack for that street activation or fireworks display were about providing right-sized audio coverage using equipment supplied by the participants. For example, use of a Walkman radio with headphones allowed for the soundtrack to be followed by a person wherever they went or maintain better focus on the soundtrack in a relatively noisy environment.
Bluetooth LE Audio and Auracast
The newly-developed Bluetooth LE Audio technology has opened up two key features that benefit these situations.
Firstly, Bluetooth LE Audio offers improved latency that has made it acceptable for online video games, video conferencing and similar latency-sensitive use cases. For example, the Bluetooth link doesn’t introduce any extra echo or delay in the sound during a video conference or you aren’t placed at a disadvantage when playing that real-time video game.
Then there is Auracast which Bluetooth LE Audio brought in to allow one-to-many audio broadcasting using Bluetooth technology. This is pitched at assisted-listening setups in meetings, cinema, houses of worship and similar environments where you want focused listening.
In the context of silent discos and similar use cases, there was a demo event that took place in Japan to prove Auracast’s worth in this use case. Here, the event known as the Silent Awa Odori worked similar to a silent disco using wireless headphones and earbuds rather than the traditional approach of a PA system playing the music loud. This avoided the intrusiveness of loud music on other non-participant communities.
The arrangement used Auracast to distribute the sound and allowed users to use their own Auracast-capable headphones or earbuds. There were two “channels” with one being the Awa Odori folk music and the other being sets performed by local DJs. It became a way to demonstrate what Auracast can do in this use case: many participants using their own devices to listen to the event’s soundtrack; support for two or more different soundtracks that are run concurrently with a seamless switchover at the user’s device; having the music perfectly synchronised thus providing a coherent experience for the participants.
This is very similar to the typical silent disco use case where it’s primarily about dancing to the music played through multiple sets of headphones with the idea of the multiple dancers dancing to the same beat at the same time. But it could be about supporting multiple events such as at a music festival.
Taking it further
With the likes of JBL offering Auracast-capable speakers including the first widely-available Auracast-capable party speakers, I see the concept being taken further. Here, you don’t need to focus on the “silent” aspect of these events but have hybrid events that use speakers and headphones but are focused in small areas. This can be about using multiple appropriately-sized Auracast-capable speakers or Auracast-capable receive adaptors connected to appropriately-sized sound systems to provide the right amount of sound coverage in an area. Here, you are using Bluetooth LE Audio and Auracast as a wireless audio backbone from the source to the sound systems or speakers.
The JBL speaker example is one that highlights Bluetooth audio-device manufacturers refreshing their audio device ranges with Auracast-capable Bluetooth silicon over these next few years. This doesn’t just apply to headphones and earbuds but to speakers and audio equipment like radios or amplifiers that have Bluetooth receive functionality.
Another direction that I see being put up is hybrid events that combine the use of on-site speakers and wireless headsets or low-powered wirelessly-linked speakers. This is more so for events where there is an emphasis on a temporary setup and there is less of a want to deal with extra cables.
The first example would be a dance party that is intended to play after a noise curfew whereupon the main speakers are shut down at the curfew time and people listen to and dance to the music through their Auracast-capable Bluetooth headsets or earbuds. Or it can be about extending the sound to other areas in a larger venue using wireless speakers that have the right sound-reproduction requirements for those areas like lesser power output and bass response for smaller rooms. The latter example may also be about having a DJ or musician perform at one location and subsequently at another location but the sound is amplified in both locations or always at the secondary location.
The second example would highlight outdoor movie setups where supplementary headsets and speakers are used to augment the movie experience, whether there is an on-site speaker system or not for the soundtrack. Here, this would be about the use of headphones or small Bluetooth speakers local to the listener’s area to provide improved intelligibility for the movie’s dialogue in high-noise environments. It can also be about movie setups that run multiple soundtracks like multilingual audio, audio description or director’s commentary tracks where the audience member can choose the soundtrack that suits their needs.
To make Auracast work better
At the moment, the theoretical maximum operating range for mains-powered Auracast transmit adaptors is 100m to 200m. This is compared to the silent-disco setups currently in operation that work on the UHF waveband and have a 500m operating range.
One feature being worked on by Bluetooth SIG for as an evolution of Auracast is to have it provide support for repeater or multi-transmitter setups that allow for wider coverage with the same programme sources that are provided through a primary transmitter. This can be in the form of a series of transmitters that cover an area but have a backhaul using a wired or different wireless technology, or a repeater that works from another Auracast transmitter. The latter situation could be supported as part of a Bluetooth speaker’s or receive adaptor’s function set which would come in handy where hybrid events are being hosted.
The user experience would require that there be a seamless handover between different transmitters running the same programme source akin to a cellular phone setup or properly-configured Wi-Fi network and that there isn’t any difference in latency when a user moves between different transmitters. This would be a key issue for repeater setups where there is the risk of latency being introduced by a repeater. As well, if a setup is about multiple soundtracks, there would be the requirement to spread all soundtracks offered through that particular Auracast setup across all transmitters or repeaters.
Another goal again being worked on as part of the evolution of Bluetooth LE Audio is what I would describe as Bluetooth audio’s “Holy Grail”. That is to provide a lossless stereo audio feed with an equivalent standard to CD audio or, better still, master-grade audio. Similarly, there would be another “Holy Grail” multichannel requirement to support surround sound to at least Dolby Digital 5.1 channel standards. This could at least facilitate multiple-speaker surround sound setups that use Bluetooth LE as a backbone.
The plans to support multiple transmitters in an Auracast setup and to open Bluetooth LE Audio and Auracast for the two “Holy Grail” setups – lossless CD-grade or master-grade stereo audio or multichannel spatial or surround-sound setups is being made as part of the standard’s future directions.
As well, Bluetooth LE Audio and Auracast would need to be supported within the automotive audio scene, whether that is through equipment installed by the vehicle builder or as an aftermarket option. This would come in to its own with the drive-in cinema use case as a digital substitute to the FM transmitter solution used in these environments. It may also be used as a means to have Auracast-based audio-sharing serve to stream multimedia content in to a car-audio setup on an ad-hoc basis. The classic example for this is to allow the equivalent of the former practice of a passenger bringing along a tape or CD to play in the car’s stereo in order to share it with the driver and other passengers during a car journey.
But the use of Bluetooth LE Audio and Auracast in the silent disco and similar use cases could demonstrate itself as another use beyond satisfying accessibility requirements for a venue.
