How does the sound get from the cell phone to the wireless headphones? – Question from Francisca Melo Dias, Sonora (MS) — Would you like to send a question as well? click here.
Seems insignificant, Sonoran guy, but for you Podcast or “going” from your phone to your ears wirelessly, there’s a complex protocol built into the tiny hardware.
Among the different methods of transmitting sound from one device to another through the air, such as radio frequencies and infrared, let’s focus on Bluetooth, which is the most popular method today.
This technology, created by the Swedish company Ericsson in 1989 for communication between computers and other devices, essentially converts audio information, originally in the form of electromagnetic waves, into a digital signal.
This signal is transmitted from the device to the earphone and converted into sound. However, the range is relatively short compared to FM radio waves, which are capable of traveling for kilometers.
The maximum distance covered by a Bluetooth signal is 100 meters in Category 1, 10 meters in Category 2 (which most smartphones are equipped with) and 1 meter in Category 3, which is sufficient for use with headphones connected to a cell phone.
An important detail: in the case of equipment with different classes of bluetooth, the limited range of technology is worth it. That is, a Category 3 phone or mobile phone will always restrict one device to another communication to a maximum of 1 metre.
You, young man from Sonor, might be wondering how the Bluetooth signal doesn’t leak to other devices and not suffer interference on the way between your cell phone and headphones. The uniqueness of the transmission is due to the coupling necessary to establish communication between the respective equipment.
Interference with other Bluetooth signals, in turn, is circumvented by changing the transmission frequency 1600 times per second (there are 79 possible frequencies between 2400GHz and 2485GHz). This way, the unlikely interference between nearby devices, even if it does happen, will last for a fraction of a second, unnoticed by your ears, Sonoran guy.
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