Capturing Sound in the Field
With the advent of mp3 players, portable audio has become a household convenience. Lots of mp3 player brands have built-in microphones, and you can even go to the store and find several models for $20 or $30 that will do the job.
But recording “Great Idea No. 312” is about all these little devices are good for. Capturing good quality sound from a high-fidelity source for your indie filmmaking project is going to take more than a click-and-go digital pen.
Again, while it’s tempting to throw in reviews of specific devices of this type, I’ll refrain from doing so and instead provide you with some general guidelines so you can go to any store or website and be prepared to make an informed decision.
Bit Depth and Sample Rate
The digital standard for full quality audio recording is 24-bit @ 96k. That means that the bit depth, or the depth of the audio quality, is equal to 24 bits. The higher the bit depth, the larger the fidelity stored each time the audio is sampled. The sample rate, or the number of times an audio sample is taken per second, is 96,000.
CD Quality audio is 16-bit @ 44.1k, and for the purposes of normal recording this is considered uncompressed. When choosing an audio recorder make sure it can perform to at least these standards. Most recorders do, but not all of them support full 24/96 audio.
Connectors and Jacks
Consider how the recording device accepts input. Some have built-in mics, but it can be much more convenient for you if the recorder has the capability to connect to other microphones you connect to it. This could be done with 1/4″ TRS jacks, 1/8″ mini-plug jacks, or XLR microphone jacks.
There are a number of converters available for changing one type of connector to another, but be aware that if you want to use a condenser microphone the unit will need to provide phantom power.
Your sound recordist is going to want headphones so that he can monitor the sound and make sure the signal is coming through in a strong and consistent manner. Check whether the device you’re considering has a headphone output jack for this purpose.
There are two basic types of microphones: dynamic mics and condenser mics. Dynamic mics don’t need external power in order to be used, but they also tend to provide a much weaker signal when recording things at a distance. Phantom power is a feature that increases the voltage of an audio recorder so that it can accept input from a condenser microphone. Condenser mics do require phantom power, or you’ll get no signal at all from them (or at least an incredibly low signal) but they are the best for capturing room noise and distant sound sources.
Take note of the recording device’s storage media. Many have their own built-in memory with the ability to save data to a removable memory card. Others can be connected directly to a computer via USB or other port and will record audio directly to the computer itself.
Size and Weight
Your sound crew is going to have to operate this piece of machinery, and if you are using a single recordist armed with a boom pole, shotgun mic, and your recorder, it’s important that he is able to wear it on him or keep it close by for easy access to its record and stop buttons.
Some devices can be slipped into a pocket or clipped to a belt, but certain recorders are more bulky and cannot be carried as easily. Take this into consideration and make sure you have, if nothing else, long enough audio cables to allow your recordist to move around as he captures sound during your shoots.