DSP: the processor for sound, sensors and connectivity

A DSP (digital signal processor) is a specialised processor for fast processing of signal streams: sound, radio, sensor data and images. In phones the DSP is part of the system-on-a-chip.

A DSP processes a signal stream in real time

In plain words

An ordinary processor is a jack of all trades. A DSP is like a conductor who does one thing brilliantly: it constantly "listens" to a stream of sound or signal and processes it in real time. And it does so very efficiently, so it can run all the time.

How it works

A signal (sound from the microphone, sensor data) arrives as a stream.
The DSP filters, amplifies or compresses it in real time.
It is optimised for repetitive mathematical operations.
It uses little power, so it is suited to running constantly.
The result is passed to other parts of the chip or to apps.

Noise cancellation thanks to the DSP

Where you'll see it

In phones (Qualcomm's Hexagon DSP), noise-cancelling earbuds, audio systems, cars, modems and hearing aids. The DSP and NPU often work together.

Does it matter when buying

You do not choose a DSP separately, but you see its work: noise cancellation on calls, "Hey Google" without draining the battery, good sound in earbuds and a step counter running in the background.

Myths

Myth: A DSP is the same as a sound card. Reality: Sound is just one of a DSP's jobs.
Myth: A DSP and an NPU are the same. Reality: An NPU specialises in neural networks; a DSP in signal processing.

FAQ

Why do earbuds have a DSP?

For noise cancellation, EQ and call processing.

Does every phone have a DSP?

Yes, as part of the chip.

What is an "always-on" DSP?

A block that constantly and efficiently listens to the microphone or sensors.