To attain the best recording level, you should set your recording level as close to the permitted maximum level as possible, without reaching and exceeding that limit. Digital audio can come very close to the threshold for PML, without distorting. Recording levels for an interview shouldbebetween -12 db and -6 db which usually allows for enough headroom to account for irregular spikes in peak levels. The unpredictable nature of Oral History interviews can sometimes be a factor in the recordings. Conversations can be very quiet and then quickly escalate in volume. Because of this, you need to make sure to monitor recording levels throughout the recording once they’ve been set. Only change the levels during the interview if it’s completely necessary. If clipping occurs, don’t panic, but do gently back the levels down. Refrain from changing the levels constantly or riding. There are a variety of ways to tweak the Input levels using a USB mic, sound card and sound editing software. Some USB mics (Blue Yeti) will have a gain control function which adjusts the input level. Other configurations will require you to adjust levels through the soundcard and software programs on the laptop.
Most digital recorders will have both automatic and manual controls.
Manual Level Controls allow the operator to adjust the input level, recording level or gain manually. Although the operator will have more freedom to be as precise as possible it will generally take more time to set the correct input levels. Some digital recorders (Zoom H2) have gain switch settings of low, medium and high. Generally for interviews the gain should be set on high. You can also adjust the input level in the record standby phase with track left and track right buttons.
Automatic Level Control/Automatic Gain Control (ALC/ALG) are circuits in a recorder that determine an average optimal level. Use of one of these will minimize the risk of clipping but typically not produce as high a quality of recording as manual level control, because they boost quiet moments in the recording up to record level and thus boost background noise. The AGC on the Zoom H2 can be accessed through the Menu and the AGC/Comp function. There you can select AGC2 (Speech) for an interview recording.
A Limiter sets a threshold above which the signal will be gently pushed down in order to prevent clipping. This allows the operator to set optimal levels and minimizes noise while still protecting the recording from clipping. Some digital recorders don’t have limiters (Zoom H1). You can access the Zoom H2 limiter by accessing the digital menu and selecting the AGC/Comp function. Note that limiters are not a substitute for good input levels nor should they be used unless absolutely needed.
A Lo Cut filter is an option designed to remove low frequencies or noise floor in the recording (wind, background hum). Generally this function is found in a switch (Zoom H1) or by accessing the digital menu (Zoom H2). If you’re already recording in a controlled and relatively sound proof environment with little background noise it’s debatable that you’ll need to utilize a lo-cut filter.