What Is Signal-to-Noise Ratio (SNR) and Why It Matters for Audio Quality

Discovering SNR or signal-to-noise ratio

In this guide I’m going to talk about the signal-to-noise ratio, known in most cases as SNR. This is a fairly recurring concept for those looking for the highest sound quality, whether in professional audio equipment, home sound systems, headphones or even in the field of music recording and production. In fact, it is closely related to ANC or noise cancellation.

But why is this issue relevant to you? Understanding what SNR is and how it affects what you hear is critical to getting the highest fidelity from an audio source. If you want to delve deeper into this topic, stay with me in this exploration of the signal-to-noise ratio and its importance for those looking for the purest sound. Let’s get to it!

What is the signal-to-noise ratio or SNR?

The signal-to-noise ratio, also known as SNR (Signal-to-Noise Ratio), is a basic concept when we talk about any system that handles signals. In any case, it is in the world of audio where it takes on special relevance. To put it simply, SNR is a measure that compares the power of a desired signal, in this case, the sound to be heard, with the power of the unwanted background noise that is present in the same system.

So that you understand, I will give you an example. Think for a moment that you’re trying to hear someone speak in an auditorium. That person’s voice is the signal. Why? Because that’s what you want to listen to. However, in this same auditorium there are other sounds: the hum of an appliance, the murmur of other conversations, the noise of street traffic… Since what you have come to hear is the voice of the person giving the lecture, all these sounds are considered noise.

Well, taking into consideration the previous example, the signal-to-noise ratio or SNR is the way to quantify to what extent the speaker’s voice (signal) is imposed with respect to all that ambient noise (noise).

How is SNR quantified?

SNR is expressed in decibels (dB). But is a high or low ratio better? In short, the ideal for those looking for the highest purity in audio is that the signal-to-noise ratio is high.

A high SNR value means that the signal strength is much higher than the noise power. Going back to the example of the auditorium, a high SNR would be like the speaker talking to you very loudly and the background noises were very low. This is the perfect scenario, as the signal is what you’re really interested in hearing. Noises are nothing more than nuisances, but if the signal-to-noise ratio is high, it means that they are hardly present.

Conversely, a low SNR indicates that the signal and noise have similar powers, or even that the noise is more powerful. This would be as if the person were talking to you very quietly and the noise in the room was very loud. You’d have a hard time distinguishing their voice in the noise, making your experience very bad.

The most common scale for measuring SNR is this:

• > 40 dB. Excellent. Very strong and clear signal compared to noise.
• 25 dB – 40 dB. Good signal-to-noise ratio. Suitable for most applications, including high-quality streaming.
• 15 dB – 25 dB. Acceptable, but low. The signal is distinguishable, but the noise begins to be significant.
• 10 dB – 15 dB. Very low. The noise is almost as loud as the signal.
• < 10 dB. Insufficient

The origin of the noise

As I mentioned above, the signal is the music, voice or any sound that is being recorded, played or transmitted. Noise can come from a variety of sources within the audio equipment itself. This happens in both headphones and amplifiers, passing through one of the key computer components in this regard: the sound card. It is a detail that must be emphasized. In no case are we referring to external noise, such as the sound of cars in the street or the screams of children in a park.

Within the SNR, the noise always comes from the audio device itself. Some of the causes and sources are these:

• Noise generated by the device’s own internal electronics.
• Electromagnetic interference picked up from the environment, such as power lines or other devices.
• Quantization noise, which appears when converting analog signals to digital.
• Humming or humming noise, often related to the frequency of the power grid.
• Hiss noise, a high-frequency background whistle.
• Crosstalk, when a signal from one channel “sneaks” into another.
• Thermal noise, caused by the agitation of electrons in components.
• Trip noise, related to current flow.
• Mechanical or vibration noise in physical components.
• Ambient noise picked up by microphones.

How SNR influences sound quality

Now that you know what SNR is and what its main causes are, I show you how it directly influences the quality of the sound we hear. A good signal-to-noise ratio is critical to a high-fidelity listening experience.

In fact, it has a profound impact on other key aspects in the field of sound:

• Clarity. A high SNR means that the audio signal, whether music or voice, stands out clearly against the background noise of the system. The result is therefore cleaner and more detailed sound. A low SNR makes noise more present and makes sound feel less crisp.
• Noise floor. The signal-to-noise ratio is tied to the noise floor, which is the minimum level of sound that a device can play without system noise being annoying. A high SNR means a low noise floor.
• Dynamic range. In addition, a high SNR contributes to a greater effective dynamic range, allowing both very low and very loud sounds to be clearly appreciated, without the former being lost below background noise.

In closing, here’s a timely reminder: there’s no point in having an amplifier with an exceptional SNR if the audio source is of low quality, such as an MP3 file with high compression. Nor if other system components, such as speakers or cables, have limitations in this regard. The audio device is just one piece of a chain in which many other links participate. So, in addition to the signal-to-noise ratio, it is necessary to verify the quality that the rest of the elements are capable of providing, as well as the audio source used. As you can see, it’s not something you’re going to look at when buying a Bluetooth speaker, but when getting a hi-fi audio system.