Recording & Digitizing sound #2

What are the four main components in an acoustic recording set-up?

1. Receiver (microphone)

2. Preamplifier

3. Digital recorder

4. Data storage

What are receivers and what do they do?

- Sensors that measure sound pressure (some measure particle velocity)

- Convert acoustic pressure into electrical energy (voltage)

- Types: Hydrophones, Microphones, Geophones

What is sensitivity in receiver characteristics?

- How much pressure produces how much voltage (dB/V)

- Need more sensitive receivers for lower-amplitude sounds

What is directivity in receivers?

- Measure of how directional a receiver is

- Measured using (DI) Directivity Index

- ↑DI = better at recording soundd

What is frequency response?

- How the receiver responds to different frequencies

- Summarized in a freq. response curve

What is bandwidth in receiver characteristics?

- Range of frequencies a receiver can respond to & produce meaningful, accurate signals

- Characterized by where there is a "flat response" (+/- 3 dB)

- Sounds you're interested in (freq.) needs to be in bandwidth of receiver

What is dynamic range?

- Range of amplitudes the receiver can respond to (lowest + highest amplitudes) - dB

- In dynamic range: accurate recording

- Exceeds range: results in clipping

- Needs to be broad enough to record lowest + highest amplitude sounds

What is Automatic Gain Control (AGC ) and what are its pros/cons?

- Recorder automatically adjusts gain in response to sound level - avoids clipping

- Advantages: Reduces clipping

- Disadvantages: Reduces value for research purposes

- It's automatically reduced, so you can't calculate sound pressure level from voltage