I understand that both devices are equipped with Bluetooth modules, but how the sound is able to play instantaneously baffles me.
In: Technology
Your phone has a machine in it that creates precise light beams that pulse in a coded pattern that are too small for your eyes to see, and your ear buds have a machine that can detect and decipher this code. Your ear buds instantly transfer this code to another machine that takes that code as a recipe that is used to beat a miniature array of drums of all different sizes that can make any sound your ear is capable of hearing if the recipe is just right. That’s also why modern country music sounds so bad when you play it- they got the recipe wrong when they recorded the music and your phone/earbuds can’t fix it- they can only play the recipe they are given.
You phone encodes sound that needs to be played for a very small period of time, dozens of milliseconds. Then it really quickly send it to earphones, typically in dozens to hundreds of microseconds. Then earphones start playing it, but as the process of buffering some data and encoding/sending/decoding is smaller than a chunk of sound to play, you don’t notice the delay.
It’s easier for music, but a little bit more complicated for a speech. They use smaller chunks of sound to the encode it, and more aggressive codec (which is kind of similar to archiver algos), so delay keeps below 50ms. Specific high-compression algos are also the reason, why music sounds much better, than speech in BT headphones (you can dive into details by reading aptX vs SBC).
Fundamentally it is just a radio transmission of data from your phone to the earphones, but there is a reason it took years to go from radio sets to Bluetooth headphones. Those chips are doing a lot and the process is very layered. How do you account for all the other signals bouncing off walls etc? How do you encode the sound as data efficiently? What do you do if you lose a packet of data? How do you minimise the power usage so an earbud works for a whole day? And a bunch of other issues that all got solved and standardised one by one to produce what essentially seems like magic. But yeah, radio waves.
Bluetooth sends information through radio waves. The reason the sound plays instantaneously is that radio waves move at the speed of light (technically they are the same thing as light), as well as the fact that the bluetooth chips are encoding and decoding the information very quickly.
The next question you might have might be, how is the sound so much better than something like, say, FM/AM radio? One is that the data is compressed into a digital format instead of analog like old school radio. Bluetooth is also a much higher frequency. This makes it worse for sending information long distances, but you can pack a lot more information into the signal, resulting in better quality audio. There’s also lots of little engineering things going on that help clean up issues you run into with wireless data transmission: interference, lost data, etc.
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