What to look out for in a sound effects library

As a sound design and production company, Sound Librarian has been using a variety of our own recordings and commercial sound libraries for many years. The world is a big place and although we’d love to record every sound ourselves, sometimes the budget, timeframe and demands of a project mean we need to source sounds from a library.

There are many excellent libraries out there, but we’ve recently started coming across some, let’s call them, “sneaky cheats” in some of the libraries and sounds we have purchased.

This is an unfortunate discovery, and maybe it’s a casualty of the growing ease of acquiring recording equipment and web-based distribution. The marketplace for sounds has become more than a little crowded.  So here's a quick guide to help you avoid the sneaky cheats and get the right library for your project.

Quality
The first thing you need to check out is the quality of the sounds. A good sound library should provide you with the ability to see a sample of the sounds included. If not, many vendors allow you to purchase individual sounds, which is a good way to get a solid idea of the quality you’re going to be getting.

Ideally, you’re going for the highest quality source material you can get your hands on. You can always down sample or compress later; you can’t go the other way.

Look for uncompressed 24bit/96kHz. This allows you to format to the standard you’d need for AAA games, film postproduction or whatever other format you require down to mobile or YouTube.  Start with the highest quality and give yourself more flexibility.

Length
Length of sounds can be important depending on what the sound is. If you’re acquiring a selection of gunshot sounds, then you won’t be looking for anything longer than the impact and tail, which in most cases would only be at most a few seconds long (if there was reverb or echo).  If, however, you’re wanting ambient sounds like wind or rain, machinery or a campfire, then a sound effect that is only a few seconds long is going to be painful. If you’re wanting to loop the sound, even the least observant individual is generally going to notice a 3 second loop.  Look for something at least 60 seconds long, or better, 5 minutes! You can always trim down the sound file later if you need to.

Length of sounds is where you’ve really got to be aware of sneaky shenanigans. Take a look at the following couple of screenshots. What do you see?  They are labelled as 60 second sound recordings, but if you take a look at the peaks, something strangely familiar is visible.  

In reality, what we have is around 5 seconds of unique recording that has been looped.  In the above case very basically looped.  The following example has tried to be creative and done a bit of reversing and creative cutting, extending the duration of the sound (sort of), but still essentially cheating.

Now one can certainly understand that if you’ve only got five seconds of clean recording and need to loop creatively to make it work in a project. But when you’re doing that and then selling it as a 60 second sound file, that’s dishonest at best and fraudulent at worst.

So when you’re looking for longer sound effects, take a careful look at the sound file and listen to it, because you may not actually be getting what you’re paying for.

Loopability
On the topic of loops, most projects that need long ambient sounds or natural environments may actually need some nice looping sounds. If that’s what you’re after, it’s great to get a nice, even, sound recording that doesn’t have an easily noticeable sound in it, like a creak of a branch or bird cry. A quick look at a sample sound file that’s advertised as good for looping will show you pretty quickly if there are any inconvenient peaks that will call attention to the loop.  Sometimes you can just cut that bit out, other times you can't. Either way, it's not an ideal situation for you as a buyer.

Noise Contamination
This should be pretty obvious, but part of having a quality sound effect is having a clean sound effect.

So if your lovely rainfall sound recording includes the sound of an aeroplane flying past, or cars on the road, that’s not going to do you any favours when designing sound for a historical or remote setting. Sometimes rain and cars is appropriate, sometimes not. Ideally, what you’d have in library is a nice clean rainfall recording on various surfaces as well as some traffic recordings and the ability to combine the two. This is just one example, the point is that much like down sampling, you can combine different sound effects together, but generally you can’t separate them out of the original recording.

Another issue would be hissy noise, if the levels weren’t set right for the recording in the first place. A kitten meow that comes along with enough hiss to sound like you’ve left the gas on is not going to be the most useable sound.  Check the quieter sound recordings for noise before you buy if possible.

Format
Anyone with a half decent editing program can convert a Wav or AIFF file to pretty much any other format you might need. Unfortunately, some sound libraries boast of having an awesome number of sound recordings, but when you dig a little, you realise that the 10,000 individual recordings you thought you were buying is actually only the same 2,500 sounds presented in four different formats.

Somehow that just doesn’t seem like value for money.

Encoding
Speaking of format, beware of the lossy nature of some formats. MP3 is a lossy format, because it encodes the properties of the sound over time in ~1152 sample chunks in a compressed form. In other words, compression means your sound quality is going to be reduced.

The best libraries should be giving you either WAV or AIFF files of all sound recordings at a bare minimum.  Other formats are a bonus, but as I said before, the same sound recording in a different format is not really an extra sound.

Variation
Having several variations of the “same” sound is an incredibly valuable tool for sound design, especially for interactive projects like games.  If your main character is going to be walking around a lot, or firing their shotgun repeatedly, then it kind of helps to have more than one sound for footsteps and gunshots.  Depending on the detail of your game, you may want to even have different sounds for bullet casings hitting different ground surfaces.  Look for a sound library that will offer you a selection of different versions of the same sound. Randomizing the play order of five gunshot sounds along with added randomization of pitch and volume can create a great level of variation in your project. The same applies to footsteps or other frequently encountered sound effects.  

So when you’re selecting a library that you think has the sounds you want, check the list of recordings and see if you’re getting 10,000 completely unrelated sounds, or are you getting nice clusters of similar sounds that you can use.

Age and Suitability of Content
When selecting a sound library, consider the setting of your project.  If you’re creating the sounds for a modern battlefield, then you are not going to have much fun if the firearms in the sound library are all antique canon and blunderbusses. Conversely, if you’re making a 1800s Western, then the sound recordings of a modern semi-automatic pistol are not going to be useful.  The same would apply to pretty much anything mechanical, be it a car or an aeroplane.  

Beyond age, again, if you’re creating a battlefield, then a collection of shotguns and hunting rifles isn’t going to be particularly helpful.  A sound library of 1000 car sounds is not going to work if they are all of 1960s sedan cars from America when you are designing for a modern project set in London.
Speaking of region, sound recordings from different parts of the world also make a difference. We spent some time living and recording in Japan, and even little things like the sound of traffic signals or railway crossings is completely different to what you hear in Australia or the USA. The same or similar animals can also sound quite different.  

Seagulls in America and England sound significantly different to those in Australia, as do crows (chickens are pretty much the same everywhere, though).  Make sure the library you are getting has the right sounds for the location of your project.  That said, it can be awesome to have sounds from somewhere different if you’re going for a location exotic to your audience.  Indianna Jones: The Raiders of the Lost Ark has a great scene where Indie is in the Peruvian jungle, and they’ve used the sound of an Australian Kookaburra to make the scene feel more exotic. That works for pretty much every audience (except Australians who may just be a little confused).

One final consideration would be the age of the sound recordings in the library. Sound recording technology has advanced considerably over the years.  Older sounds may have been recorded with older equipment that gives less depth to the sound, or you may end up with mono sounds when you’re looking for stereo.  On the other hand, you could end up with some truly unique sound effects that are no longer even possible to obtain! Imagine if the technology had been available to record the voice of the Dodo as well as the image.

So when you’re looking at a library, check when the recordings were made, and be sure that you’re getting the best value for their age.

On the whole, sound libraries can be an invaluable resource, allowing you to produce great content quickly and to focus your time on the unique sound effects that really make your projects stand out.  

With the crowded marketplace of free and paid sound effects libraries out there, it pays to be aware of the potential sneaky cheats, shortcuts and other considerations so you can direct your buying power in the right direction.