The power of metadata in audio files

Find what you’re looking for - The hidden power of Metadata

Your audio files contain powerful hidden data that you should know about. While most metadata are not visible at a glance the application you use, in this case an audio or sound library application, will often be able to display and manipulate all the metadata you need. For many of us that work with metadata we appreciate just how important this data is in our daily work.

I have spent many hours building and maintaining the ever-expanding SFX libraries of Radius360 and the various companies I’ve worked for to make them as effective as possible to use. I would like to share a little bit of the insights I’ve gained during this process, in order to help make your library and process of organizing sound assets more productive.

Let it be known that I’m no technical expert on metadata data. I have some technical knowledge, but I am primarily a creative user that has learned technical skills by way of necessity in order to improve and increase my creative output. I would love to hear how you manage and incorporate metadata into your workflow or add to the points I am making.

For the purpose of this article I will limit my description of metadata to how it applies to audio files, specifically sound effects and will only briefly touch on music files as it is an important tool for sound design and music supervision.

It can be difficult to find the right sounds when searching within an SFX library. Why? It is often due to poor or missing metadata.

What is Metadata?

Dictionary.com has a good description; “a set of data that describes and gives information about other data.”

“descriptive metadata (Guide metadata) also contains valuable information with regards to the content of the file, such as a detailed description and keywords. Both of which are essential to get successful hits when searching a library for a specific sound.”

In the case of audio files, aside from technical information such as file type, sample rate and format, the descriptive metadata (Guide metadata) also contains valuable information with regards to the content of the file, such as a detailed description and keywords. Both of which are essential to get successful hits when searching a library for a specific sound.

While the vast majority of commercial SFX libraries employs proper file naming such as gunshot.wav, applause.wav etc., the filename still only tells us: what type if file it is such as .wav, .mp3, etc., and brief description as part of the filename about what type of sound it is.

Filenames are usually relatively short, so they do not give enough detailed information for us to get effective search results. Let’s use the filename example, “gunshot.wav”. Based on the filename we know it’s a gunshot, but what type of gun? Which make/model, category i.e. vintage vs modern?

The advantage of Metadata is it can contain all this information and more.

How does metadata help improve my sound design?

Being able to effectively narrow down your search to a granular level is crucial for the gathering of elements used in sound design by being able to identify the sounds to match to specific objects, as an example being able to identify sonic qualities, time periods and locations such as a city or country.

Working with metadata.

In the case of audio files such as .wav and .mp3 the metadata is embedded within the file and not stored as an external file as you may see in .xml files for image files, so it is very easy to manage. Depending on the application you can embed the metadata permanently into your files. In the case of your own recordings or non-commercial libraries the descriptive metadata may be missing partially or completely, and you will have to enter the information manually.

Creating good and consistent metadata habits are important when managing your library and will save you countless hours by improving your search results.

Depending on your audio application large batches of metadata can also be completed by importing data from spreadsheets. The advantage of using spreadsheets is you can use the powerful tools in applications like Microsoft Excel to apply to a large number of files at once.

Whether handling in batch or individual files it is important to get in the habit of taking a copy of your raw recordings and embed the appropriate metadata when adding to your library. I use Soundminer Pro which is very effective at handling large amounts of files and data but every application is different so please check your audio application to see which features it has for handling metadata.

Creating efficient descriptive metadata (guide metadata):

Some library applications may use a thesaurus to widen the search results. As a result, searching for the word “airplane” may also yield a search result of “aircraft”, “plane”, “jet” etc. That helps but may still not be as specific as you like and depending on the size of your library that can result in too many results coming back. But it may still be worth considering to manually enter associated words, so the metadata still works for you in applications that do not employ a thesaurus.

“It can be useful to make that association in your metadata, so you get inspired results and avoid nonlinear search results.”

What I have found helpful when creating my custom metadata is to enter specific keywords that I personally associate with a sound or know could be useful later. For example, there are sounds that are excellent to layer or use in conjunction with other sounds that may not be readily apparent. A metal light switch could work as part of an initial button on a weapon, or a drill could be part of a larger mechanical item like a robot. It can be useful to make that association in your metadata, so you get inspired results and avoid nonlinear search results.

"You say tomato, I say tomato" – Spelling and language.

When entering your data, it is very important to use spellcheck. Misspellings are the bane of any good SFX library, and I have seen misspellings even in commercial libraries. Also keep in mind U.S. vs British spelling; “center”, “fiber”, “theater” vs “centre”, “fibre”, “theatre”, etc. English is not my first language, so I also include words I associate with my native language in the metadata using the English translation in order to have it work with English databases. However, how you associate is what is important, and it is really down to making the data work for you.

“Concise and precise is the name of the game.”

In the description field I tend to be descriptive but not enter entire spoken sentences. It takes too long to read and usually do not yield much benefit when searching for sounds in my experience. Concise and precise is the name of the game. Any unique features in the sound should be mentioned. For a location recording I use metadata that includes country, city, date and time, such as rush hour, distance, technical details such as microphone set up and any other characteristics that comes to mind.

The keyword field can be used to associate a sound with categories, so you get a hit on a wide search result using a keyword. A keyword for a particular weapon can fall under the categories of weapons, sci-fi, vintage, western, war, medieval, etc. Searching on keywords helps me to collect lots of assets pertaining to a specific category. In the case of a battle scene I may need battle cries, weapons, and ambience, which all could be associated with the keyword battle or warfare, etc.

Let the music play.

This article was primarily for working with metadata for SFX. For music files the metadata fall under the ID3 tag and includes data such as copyright, license, genre, composer, etc. I occasionally supplement the existing metadata by entering similar composers or genres which can be helpful for cross reference when working with sound design.

This was just a brief outline of the power of metadata as it pertains to audio files within a SFX library. I hope you get the bigger picture and you’re able to apply this to your files to improve your sound design. Please feel free to leave a comment or suggestion. I would love to hear of your metadata tips and tricks.

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This is important information that is usually overlooked by new authors. Very good explanation, Rad360.

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Hello Radius360:
Thank you for your article " The power of metadata in audio files"
My name is Eric Zimmermann. I am a composer in Los Angeles.
Do you submit recordings to libraries for use in film production?
I would like suggestions of libraries or music repositories that I can submit my recordings to for placement in film & television projects.
Sincerely, Eric

Thank you for your contribution to help others! I hope this helps some one. Its great to help others!