How to Record Sound Samples – Moeller Studios

This is a tutorial on how to record sound samples. It is primarily intended for people who want to record sound samples in a variety of locations for use in electroacoustic music.

Find a good place to record

Acoustics and ambient sound impact what is captured during a sound recording. Here are a few things to consider:

Avoid unwanted acoustical effects:

Reverberation is essentially impossible to remove from a recording, but easy to add in post production. Consider recording in an acoustically “dry” place (i.e., a place where sound reflections are minimized) and add reverb later. These same principles apply for echo, which is simply a discretely perceived reflection. Mic placement and pickup pattern can help minimize the amount of reverb that is recorded (see below). In some instances you may want to record reverberation; for an example, see the notes below on concert-recording techniques.
Smooth, reflective, parallel surfaces (i.e., facing walls, or ceiling and floor) can lead to an acoustic phenomenon called “flutter echo.” Clap your hands around the space and avoid any spots where you hear flutter echo (i.e., a funny “boing” sound). Alternatively, put absorptive material on the surfaces that are parallel to each other.
Remove or dampen objects that resonate sympathetically with your sound source and add undesired sound to your recording.
Be aware of the resonances in the recording space itself (i.e., room modes). For example, a small, box-shaped room may unduly emphasize certain low-frequencies. If possible, avoid recording in a space that resonates in an undesirable way. See the points below about placing the sound source and the mic in the space.

Avoid undesired ambient sounds:

The best method is to avoid recording unwanted sound in the first place. However, close miccing and directional mics can also help minimize picking up unwelcome ambient sounds (more on this below). Various post-processing techniques can also be helpful.

Place the sound source

Start playing the sound source in the middle of the space, away from anything else, and where the ceiling (if any) is highest (albeit avoiding any ceiling features that focus the sound, such as domes or peaked ceilings). Move the sound source around the space until you find the best sounding spot.

Choose the mic

Make your selection while bearing in mind the following:

Directionality:

Directional pickup patterns can reduce unwanted sound from the null areas of the mic.
Spectral coloration can occur to the sounds recorded off-axis using a directional mic.
Increase in low frequency due to a phenomenon known as “proximity effect” must be considered with directional mics. If it is problematic, increase the distance between the mic and the source, or roll off the low frequencies using a filter.
Directional mics can increase the ratio of direct to indirect sound (i.e., a directional mic at the same distance as an omni mic will pick up less indirect sound, such as reverberation and ambient sound). This allows the mic to be placed further from a sound source, allowing all the elements of the sound source to combine in the air before being picked up by the mic, potentially resulting in a better representation of the sound (more on this below).

Type:

Condenser mics generally have a better high-frequency response than dynamic mics and can respond to transients faster. That is because the diaphragm of a condenser mic is lower in mass and travels less than that of a dynamic mic.
Dynamic mics are generally more robust and can handle higher sound pressure levels before distortion occurs. However, condenser mics sometimes have built-in pads that can attenuate the signal before overloading the internal circuitry, thereby making them potentially usable in high-sound-pressure-level situations.

Additional Considerations:

Mics have different frequency responses. Take a look at the manufacturers specs and consider how each mic will color the sound. For example, the frequency curve of certain mics have become popular for recording vocals; or, the frequency response of some mics are intended to account for high frequency loss due to distance.
If you are recording outdoors, a basket and furry windscreen around the mic is recommended to ameliorate wind noise.

Place the mic

The closer the mic to the sound source, the less reverb will be picked up; however, it is usually best to give some space between the mic and the sound source to allow all the contributing elements from the sound source to combine naturally in the air before being picked up by the mic.

The following two tips come from Bobby Owsinski’s The Recording Engineer’s Handbook, 3rd Ed., p. 79:

For an omni mic, cover one ear and listen while you move around the sound source, place the mic in the spot where it sounds the best.
For a cardioid mic, cover one ear and cup your hand behind the open ear and listen while you move around the sound source, place the mic in the spot where it sounds the best.

If recording multiple sound sources at the same time using multiple mics, remember the 3:1 rule, namely, each additional mic should be placed at least 3 times the distance from a sound source that already has a mic on it. This minimizes phase issues (i.e., the inverse square law ensures that the delayed sound reaching the additional mic is quiet enough that it minimizes comb filtering when combined with the signal from the first mic).

It is easy to work in mono, and it is simple to add spatial effects later. With that said, there are a variety of stereo mic techniques useful for capturing spatial information (mid-side, coincident, near-coincident, spaced pair, and binaural, and all their variations). This is beneficial for such things as recording large sound sources where you want to retain the spatial placement of the contributing sound elements (e.g., a piano, an ensemble, a soundscape, etc.). There are additional approaches that can also yield worthwhile spatial results (surround mic techniques, a SoundField mic, and so forth).

Concert-recording techniques are intended to capture the sound source and the sound of the concert hall while retaining a sense of the spatial image. The aim is concert realism. Stereo or surround mic techniques are typically used. Additionally, the mic array is usually placed a distance away from the sound source in order to capture both the direct and reflected sound; frequently, this means placing the mic array at the critical distance from the sound source (the critical distance is where the direct-sound level and the reverberant-sound level are equal). In addition to horizontal distance, it is also common to place the mic array at a height that is above the sound source (thereby minimizing reflections from the floor, sounds from the audience, and on-axis blasts from some element of the sound source).

Set up the recording device

Set the recorder to record in an uncompressed (PCM) format (some lower-end recorders allow you to record in various compressed formats). This means using a format such as .aif, .wav, and so forth.

Set the sampling rate, and bit depth.

The sampling rate is how many times per second the amplitude of the input signal is sampled. In practical terms, the sampling rate has a direct bearing on the frequency range of the signal (i.e., you can record frequencies up to half the sampling rate).
The bit depth determines the quantization resolution of the instantaneous amplitude of the sampled signal. With a bit depth of 24, the number of possible amplitude levels that the signal can be represented by are 2^24 = 16,777,216. In practical terms, the bit depth has a direct bearing on the dynamic range of the signal (i.e., about 6dB per bit). In theory, a 24-bit system would have a dynamic range of about 6dB*24 = 144dB (although in practice, the A/D converter may limit this).
Consider using 96 kHz, 24 bit.

Turn the input gain down all the way, then plug in the mic.

If using a condenser mic, turn on phantom power.
If using a dynamic mic, phantom power is not necessary.

Set the level on the recording device so the meter shows a strong signal, but make sure it doesn’t “clip.” As you perform the sound, strive for a high “signal-to-noise” ratio, in other words, make sure the desired sound is louder than the unwanted ambient noise floor.

Record

Tips:

Record several iterations of each sound (if possible).
Let each sound iteration die out completely before recording the next one.
Monitor what you are recording.