How far is airpods Bluetooth?

At WWDC 2020, the functions of Apple AirPods were fully upgraded. One is the seamless switching of headphones between multiple devices, and the other is the "spatial audio" function. Apple claims that the updated AirPods can sharply distinguish the direction of sound and present the effect of "panoramic sound".

In September, iOS 14 was finally released as scheduled, and Apple also pushed the spatial audio function for AirPods Pro as scheduled, but after the trial, Lei seemed even more confused. ...

"Spatial Audio" Experience

First of all, let's introduce Apple's statement about spatial audio: As long as you update AIrPods Pro, AIrPods will automatically remember to adjust the direction of sound at any time according to the swing of your head. On traditional headphones, if you tilt your head, the sound you hear will inevitably follow your head, which is undoubtedly in line with public cognition.

Through spatial audio technology, Apple has achieved a cinema-like experience: no matter how biased you are, all sounds will be emitted in a fixed direction by default. If you move your phone, AirPods Pro will also adjust the sound field of the "sound source" accordingly.

Let's not talk about the principle, let's talk about the effect. In the official version of iOS 14, Apple pushed the new firmware 3A283 to AirPods Pro users. Just connect AirPods to the device of iOS 14 for half a minute to listen to music. Put AirPods in the box cover and charge it with a charging box with a cable for about half an hour, and the headset will be automatically upgraded to the new firmware. If it fails, please try again.

After the update, you will find that a switch named "Space Audio" will appear in the setting interface of AirPds Pro, and a space audio switch will also appear when you press the volume option of AirPods for a long time in the control center. After the first audition, Xiao Lei had to admit that space acoustics really achieved the publicity effect of Apple.

In traditional stereo audio playback, you can roughly tell the direction of the instrument, but after switching, the direction of the instrument will become extremely clear. For example, the sound of sand hammer in the audition music seems to be fixed in front. No matter how you turn your head, the position of the sand hammer will not change. If you turn your back to your mobile phone, the instrument will ring in the back and play in a fixed corner of the room all the time.

Metaphorically, some voices have changed from "voices in the brain" to "voices in front". Sometimes, you will mistakenly think that AirPods Pro can't connect the headphones, but the phone speaks with the speaker in front.

The audition alone is so shocking. What kind of power can AirPods Pro show in real movie scenes? Apple claims that space audio needs audio and video resources of 5. 1 or 7. 1 channel. At present, some mainstream websites in China can enjoy the benefits of spatial audio, such as Tencent's "Colorful Audio-visual" (Dolby Panorama), iQiyi's "Dolby Panorama" and Youku's "Enjoy Audio and Video in Frame", all of which support spatial sound effects.

Xiao Lei chose Tencent video "Cai Zhen Audio-visual" for audio-visual. By adjusting Dolby's panoramic sound option, headphones can clearly feel the azimuth difference of the sound source. But the problem is that all sounds have a sense of distance out of thin air, which truly restores the level of the cinema, but on the mobile side where the playback source is close at hand, its experience is really bad.

When watching two movies, Wolf Warriors 2 and Evil Does Not Suppress Right, as a test, the obvious sound of "several meters away" made Xiao Lei feel like watching a "gun version movie". In addition, the sound quality potential of AirPods is not high, and the algorithm of forcibly separating the sound source will only make the sound thinner.

But what's even more amazing is that when Tencent didn't indicate "dolby pro logic" in movies such as Reunion 4 (although supported by iQiyi), the experience of spatial audio function was unexpectedly effective. These films can not only effectively separate the sound, but also make the sound source close enough to really produce a sense of reality of "being in the theater". Compared with the original film, its audio-visual experience has been improved. Xiao Lei speculated that this is probably directly related to the audio processing level of major studios and the support of players. Apple TV+ has the best video audio-visual experience.

Although the actual experience of "space acoustics" is not in line with Apple's ambitious statement, the producers need to re-adjust the sound suppression strategy, which will not happen overnight. However, improving the experience of space audio is indeed the direction of major digital manufacturers in recent years.

The rise of computational audio

If you are interested in mobile phone photography, you must have heard of the term "computational photography". In general, it is to improve the performance of the weak camera component of the mobile phone as much as possible through the algorithm. Global mobile phone manufacturers have struggled for more than ten years and made great progress in the field of computational photography, which greatly improved the usability of mobile phone photography.

In addition to computational photography, various manufacturers are also making full use of computational audio to realize the experience similar to wired music in the wireless field, and even hope that wireless music will "surpass" traditional headphones and restore the live experience to the maximum extent through technological progress.

In recent years, Google, Sony, Dolby and Microsoft have all introduced functions similar to "spatial audio", among which Sony and Dolby have also introduced wireless headsets. However, from the experience of finished products, although everyone has achieved the experience of "multi-source speakers", no one can change the direction of sound source by deflection like Apple. Of course, even AirPods, Xiao Lei doesn't think it has subversive innovation.

How to use headphones to achieve "immersive" effect through virtual sound field is actually directly related to the principle of human receiving sound. People judge the distance and direction of sound, not only through the straight line propagation from the sound source to the ear, but also through several simple reflections of the sound through the wall, reverberation of many reflections, and the time difference when the ear hears the sound.

Then once the sound mechanism becomes complicated, you need to consider the attenuation curve of sound in all directions, the direction of sound source at the reflection point and so on. The formation and listening of sound is a very complicated situation, which is difficult to simulate with current hardware and algorithms.

Fortunately, in addition to the consumer gradually optimizing the algorithm for calculating audio, the producer also noticed the importance of spatial audio. Mei Tian Studio in China once demonstrated the technical exploration of "spatial audio" and applied some of its achievements to the mobile game Call of Duty. On the mobile phone side, the spatial audio experience of different scenes and different materials is initially realized, so that players can better use their hearing to identify the position and knock down the enemy.

The future of space audio

In fact, the reason why Apple, Google, Dolby, Sony and Microsoft are so committed to studying space audio is because VR is basically an unavoidable one. With the release of a series of VR games with extraordinary quality, such as Half-Life: Aylx, traditional stereo has been unable to optimize the audio experience of the game, and manufacturers need to bring more realistic sound simulation in the VR world.

In the field of MR (Mixed Reality) that Apple and Microsoft focus on, space audio based on reality is undoubtedly more attractive. In larger-scale scene simulation, spatial audio is beneficial for users to explore more easily. Although Apple has the best sound effects at present, Lei has reason to believe that these manufacturers will soon come up with experimental technologies beyond AirPods.

I hope that one day, Xiao Lei can get rid of the general space audio experience of "watching pirated movies".

Report/feedback