Can You Hear if Audio is Watermarked? 3 Watermarking Technologies Explained

by Intrasonics Team

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Audio watermarking is the process of adding an electronic identifier that is embedded into an audio signal, but can it be heard?

The short answer is, it depends. In this post, we explore three popular technologies and answer that question for each.

Why is Hearing Audio Watermarking an Issue?

Watermarking is commonly used to help identify who owns the copyright, but a challenge that has surfaced for many companies trying to protect their audio, is also protecting the experience of their consumers at the same time.

Like watermarking physical documents and photographs, it is essentially a way of embedding information onto a signal that is difficult to remove.

The big difference between audio watermarking and physical watermarking, is that although it is generally acceptable and not distracting to see a physical watermark on a photograph or other document, hearing an audio watermark can be disruptive and ruin the quality of the audio.

Particularly as companies like Universal Music Group use a watermark on the tracks owned by the company that they provide to Tidal, iTunes, Spotify and Rdio among others, that many users have heard, ruining their listening experience in the process.

This can become quite a big issue. Is there any way around this?

Fortunately, there are some positive options available in answer to the question of whether or not you can use an audio watermark without it being heard.

In this post, we are going to discuss some of the most common, and some more advanced types of watermark available today.

Spread Spectrum Watermark

The first watermarking technique we want to discuss is responsible for the problems users are having with UMG (Universal Music Group) artist’s releases on various streaming services.

Which artists are signed under UMG? Oh, nobody major. Just the likes of Kanye West, Taylor Swift, Jay-Z and Lady Gaga to name just a few.

Jokes aside, you can understand how many popular songs this watermark affects.

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Spread spectrum watermarking was originally used for watermarking images. As you may imagine from its name, it works by intertwining the watermark in with the content.

From the point of view of content providers worried about users removing the watermark and making it untraceable, this is something that is generally difficult to do.

Well, at least not if compression algorithms are used.

As it exists within the same range of frequencies as the original content, careful consideration is necessary when it comes to its placement.

To try and limit the amount of downgrading it causes to the audio, it needs to be inserted as a low amplitude noise across the entire spectrum.

Issues arise with it because the content needs to cover a wide enough frequency range and not everyone is insensitive in the same way to low level noise.

This is why many Spotify and other streaming service users complained that they could hear an audible hum in the audio.

Ultrasonic Watermarking

Another popular method is ultrasonic watermarking, and as you’ve probably guessed it, this involves placing the watermark outside of the auditory spectrum human ears can hear.

The ultrasonic range starts at 16Hz and beyond.

That, obviously, makes it a great choice for watermarking where you want to be able to track and make sure the copyright identifier is intact, without ruining the enjoyment of the audio it has been attached to because it can’t be heard.

However, its biggest advantage is also its biggest disadvantage, as it is deliberately placed at a separate frequency range to the original content, it can easily be removed without having an adverse impact on that original content.

This makes it incredibly ineffectual if it is needed for forensic reasons, after someone has tampered with, or removed it.

To add further problems, it is often the case with this type of watermark that removal happens accidentally during the compression process.

Ultrasonic watermarks are lost in the compression of all standard streaming services, including YouTube, Spotify, Radio and iTunes, as well as video platforms like Netflix, BBC iPlayer and other popular platforms.

Echo Modulation Watermarking

That leads to what may well be considered the best. In principle, sounds bounce or echo off any object within earshot.

We often don’t hear those echoes or bounces, because our auditory system has been designed to filter them out, particularly the short ones.

Can you imagine what would happen if we heard all the individual echoes from each object? We and our senses would be overwhelmed.

The only echoes we hear are the longer ones. That is why we can detect echoes that stretch over longer distances, for instance in a cave or a large church hall.

Echo modulation as a watermarking technique takes advantage of this insensitivity to embed the data in those short, silent echoes.

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At present, here at Intrasonics, we are the only organisation offering this as a viable form of watermarking.

When we produce an echo-modulation watermark, we take the original content, then calculate the natural echoes for that music and add the important data into those echoes.

Although artificial, these echoes have exactly the same structure as echoes created naturally and are inaudible.

You can contact us for a demo here

The difference is that these echoes are inserted in a way that allows devices to extract them to identify the watermark.

There are relatively few downsides, but lots of crucial advantages to using echo modulation watermarking.

The watermarks are extremely reliable and produce a very low incidence of false-positives, with less sensitivity when it comes to timing and frequency shifts.

What’s more, audio with echo modulation marking will still run on much slower or older hardware and is not reliant on battery-power or connectivity to a Wi-Fi connection or Bluetooth connection.

Which Audio Watermarking Technology Should You Use?

Ultimately, it’s up to you to make the choice that suits your audio best from the above options.

If you are looking to gain the forensic and tracking benefits as well as the copyright protection of having audio watermarking on your files, but don’t want to negatively affect the quality of the audio in question, echo modulation is currently the audio piracy technology that fits that mould.

It doesn’t impede the listening experience of users who are streaming or have downloaded the file, and best protects your content.

If you use anything, apart from ultrasonic and echo modulation watermarking, you will always have the potential problem of some users being able to hear the off-putting watermark.

But unlike ultrasonic watermarking, echo modulation can’t be easily removed, and the user will still enjoy the audio without even noticing its presence.

That is why, at Intrasonics, we highly recommend the cutting-edge echo modulation watermarking over and above the rest.

If you’re unsure about which solution is best to protect your audio or video content, contact us directly and speak to our team about our various services and how we can help you.

You can contact us online here.

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