ASTi Logo

Application Note

Taking Sound Recordings For Environmental Cue Model Development (#59)

Recording Guidelines and Tips

Select a microphone position as close to the operator's position and earpoint as possible since this will be the location whereby the customer judges the sound. If the platform is large and there is concern about sound levels and characteristics in other parts of the platform, consider taking the same series of recordings at different locations. Do not, however, move the microphone about during a recording sequence as this will change sounds and characteristics.

Throughout the recording process as little adjustment and interference as possible should be made to the recording equipment (no messing with recording levels or microphone position unless absolutely necessary!). If changes are necessary, they must be noted.

Record equipment settings including recording levels, input gains, and any other settings specific to the equipment. Again, minimize or eliminate changes during the recording process if at all possible.

When making a series of general sound sequence recordings such as engine states, set the recording equipment up and conduct a set of preliminary recording tests at the loudest operational state of the platform (perhaps full throttle or operation of the vehicle gun if so equipped). Set the microphone gains under these conditions such that the inputs are not saturated/clipped. Once set, do not change the record level unless the level indicators show that clipping is taking place. Always note the settings as part of the test log!

When attempting to capture specific equipment sounds for use in the sound model itself, attempt to capture the sound cleanly by removing as much background sound from other sources as possible (e.g. turn off the air conditioning for the time of the recording, record the sound with the vehicle stationary and at minimum engine RPM - or with the engine off if the sound is the same).

Also try to position the microphone for maximum rejection of unwanted sounds, usually by moving the microphone close to the sound source. Keep an eye on the recording levels to ensure the sounds are recorded loud enough, but not into any kind of clipping. A clipped recording is at best useless. Conversely a recording that is too quiet will be very hard to work with, and it may be that the required sound is masked by inherent noise in the recording equipment. Several recordings may need to be attempted to achieve the right balance.

Remember that all the useful recordings will be taken from inside the platform as this corresponds to the interior and reference point in the training device. Just because the engine is louder outside does not make this the right place to record the sound.

Be sure to review and verify all recordings while there is still access to the reference platform. Unprintable words will be spoken when the recordings are evaluated back at the office only to find that strapping the microphone to the bulkhead was not such a great idea (as evidenced by the vibration induced noise and distortion). At that moment, "Oops" probably won't cut it.