Digital Signal Processing (DSP) Audio Explained: A Beginner’s Guide

DSPs are placed inside most audio devices. But what do they actually do?
DSPs are placed inside most audio devices. But what do they actually do?

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Our beginner-friendly explanation of DSP audio and its common applications.

Digital signal processors (DSP) have been circulating in the tech industry for a few decades now, but have only recently found mass implementation in our daily audio devices.

If you’re not sure what DSP audio is, you might feel a little lost in the conversations surrounding it – or confused by the audio products on which it’s advertised.

In this article, we’re diving into DSP audio and how it impacts our listening experiences.

What Is a DSP?

A DSP, which stands for digital signal processor, is a device that takes digital signals and alters them through a series of algorithms, usually within milliseconds. This is usually found in headphones, speakers, smartphones, and other modern devices.

In audio, DSPs do a lot of things that improve our overall experience with audio devices. Features like bass boost, active noise cancellation, adaptive equalization, and voice typing are all the results of digital signal processing.

Let’s break down how a DSP actually works to gain a better understanding of how and why they are used in audio devices.

How Does a DSP Work?

A diagram showing where a DSP falls in an audio signal chain.
A diagram showing where a DSP falls in an audio signal chain.

DSPs work by manipulating incoming digital audio signals with specialized algorithms before passing them on to the next part of an audio signal chain.

As their name suggests, DSPs work exclusively with digital signals. So, in order for a DSP to process an analog audio signal, it must first be converted to a digital signal with an analog-to-digital converter (ADC).

Similarly, alterations made by a DSP are only audible once the manipulated digital signal has been converted to an analog signal by a digital-to-analog converter (DAC).

Soundwaves are moving air particles that can be reproduced as analog signals using electrical alternating current (AC). When that electronic signal is converted into digital binary, a DSP can alter the signal information to manipulate the sound.

There are several key components inside a DSP that enable it to manipulate digital audio signals:

A diagram showing the components and signal flow of a digital signal processor (DSP).
A diagram showing the components and signal flow of a digital signal processor (DSP).
  • Program Memory: Contains the program/software that a DSP will use to process data.
  • Data Memory: Stores the data that needs to be processed.
  • Compute Engine: Accesses information from program and data memory and processes the signal.
  • Input/Output: Used to gather/distribute information from/to the real world.

What Is DSP Audio Used For?

There are many uses for DSPs that help improve audio quality. Below are five common audio applications for DSPs:

Active noise cancellation (ANC)

Any and all headphones or earbuds that feature ANC use a DSP to achieve their noise cancellation.

First, an ADC converts analog signals picked up by microphones on the headphones to digital signals. A DSP then uses an algorithm to phase-flip the signals before feeding them back out to a DAC. The final result is the phase-cancellation of environmental noises.

Echo removal

Through digital signal processing, devices like your phone or laptop can prevent echoing that can occur between the microphone and speakers. A DSP is able to recognize copies of the audio it has already received or transmitted and then remove them to prevent feedback loops.

Managing phone call volume levels

A DSP is integral to keeping the volume levels of phone calls within a comfortable and reasonable range. A DSP can serve as a limiter by reducing volume when it detects particularly loud sounds or as a gate by filtering out quiet background noises.

You can imagine noise control in audio devices as a gate (hence ‘gating‘). If you whisper “let me in,” the gate won’t budge. When you yell at a higher volume, the gate will open. This principle is how DSP can help reduce unwanted noises in your audio equipment.

A DSP determines these volume thresholds by matching the input signal strength to the voltage that the output (speakers or headphones) can handle comfortably without losing volume or distorting.

Equalization (EQ)

A DSP can also be used for adjusting audio balances via equalization. Upon receiving a digital audio signal, a DSP is able to make additive or subtractive amplitude adjustments to specific frequency bands. These changes are then reflected in the audio signal output by a DAC.

Music production

It’s no exaggeration to say that every modern album has been mixed, mastered, and produced with heavy-handed help from the DSPs in DAWs. Everything from basic equalization and compression to effects like delay and reverb rely on digital signal processing to get the job done.

Does a DSP Go Before or After a DAC?

A DSP is positioned before a DAC in an audio signal chain. This minimizes the number of digital-to-analog conversions that must occur before an audio signal reaches a listener’s ears.

Remember, a DSP affects the final analog audio signal by making interventions to the digital signal. A DAC is the final point at which a digital signal is converted to an analog signal. All digital processing should occur prior to digital-to-analog conversion to maximize efficiency and eliminate unnecessary reconversions between digital and analog signals.

Should You Get a Dedicated DSP?

While DSPs are already built into a plethora of audio devices, there are certain circumstances where you may want your own dedicated DSP.

One such circumstance is if you’re using speaker monitors in an untreated room. A DSP with equalization functions can help manage wonky balance issues that stem from standing wave frequencies and room reflections.

Headphone listeners may also find a dedicated DSP helpful. Audio DSPs with EQ abilities enable a listener to find the exact balance they’re looking for, whether that means cutting the highs or boosting the lows. However, it’s worth noting that several DACs come with built-in DSPs, which eliminate the need for a dedicated one for headphone listening.

Frequently Asked Questions

Do DSPs affect audio quality?

DSPs, by design and intent, have an effect on audio quality. While some audiophiles bicker over whether or not a DSP can have an inherently negative impact on audio quality, the short summary is that if they do, you likely can’t hear it.

Are there software audio DSPs?

There are several software audio DSPs, ranging from Apple Music’s basic in-app EQ to audiophile-oriented programs like MUSE.

Can I use a DSP for audio measurements?

Some DSPs can indeed be used for audio measurements. The MiniDSP E.A.R.S. is a good example of a measurement-oriented DSP that has become relatively popular.

💬 Conversation: 3 comments

  1. “However, there is a loss in sound accuracy in the process of analog-to-digital conversion”
    This is not inherently true. It may happen. But with sufficient oversampling and proper design of the antialiasing filters the resultant signals can be virtually identical. I am not saying such is always the case. But just because it is digital does not mean the result is different.

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