| A | B |
|---|
| Sound | Is made when an object vibrates through a medium |
| Vibrating Object | Causes particles of air to move back and forth; particles in turn move other particles. |
| Eardrum | When the changes in pressure reach our ear, the vibration moves it to move back and forth. |
| Brain | Signals from the eardrum are interpreted by our as sound by this? |
| Frequency & Amplitude | They represent the vibrations created by an object; can be graphed. |
| Amplitude | Graphed as the height of the wave, measured in Hertz, shows how much pressure is created when the object vibrates; interpreted as the volume of the sound. |
| Hertz | How many times the waves move in a second. |
| Frequency | How often the vibrations happen; the pitch of the sound; quicker vibrations produce a higher-pitched sound; on a graph, shows up as the curviness of the sound’ |
| Human Ear | Slowest waveform hear is 20 hertz (a vibration that happens 20x per second); highest vibrations about 20kHz (20,000 times per second). |
| Reproducing Sound | Can be done two ways: Analog or Digital |
| Analog Sound | Works by transmitting or storing sound through physical means; transmission creates a relationship (analogy) between the input (how much sound is captured) and output (the amount of sound produced by the speaker’ |
| Digital Sound | Sound may still be captured by analog means, but the transmission and storage are done by converting the sound into binary information. |
| Binary | The language of computers. |
| ADC (Analog to Digital Converter) | What the digital conversion is handled by; scans in two resolutions that are a representation of the sound; quality of the conversion is measured in Sample Size and Sample Rate. |
| Sample Size (Sample Accuracy) | Records the Amplitude of the signal at different levels of resolution; vertical resolution of the scan; higher the sample size, the higher quality; measured in bits; CD quality is recorded at a 16-bit sample size. |
| Sample Rate | The amount of samples per second in an audio recording; the additional more accurate the representation; horizontal resolution; a sound recorded at 44 kHz (44,100) samples per second is considered CD-quality sound. |
| Bit Rate | A combination of the sample size and sample accuracy; total amount of bits that are digitized or received by a computer during a certain period of time; measured in bits per second. |
| Sound Formats | MP3 is king; usually have more than sound information; multiple channels can be stored; multiple tracks. |
| Compression | Uses mathematical algorithm to reduce the file size; can be lossy or lossless. |
| Lossy Compression | Sacrifices sound quality for file size. |
| Lossless Compression | Is not compressed sound. |
| AIFF (Audio Interchange File Format) | Developed by Apple; flexible, allows for various sample sizes, rates, number of channels, lossless. |
| WAV (Windows Wave) | Developed by Microsoft; flexible, allows for various sample sizes, rates, number of channels; lossless. |
| MP3 (MPEG Audio Layer 3) | Developed by Motion Picture Experts Group; lossy, but excellent quality; works like jpeg by understanding that not all the information in a sound is necessary for people to hear them well |
| Microphones | Capture the vibrations in the molecules and convert those sounds into signals; two important characteristics: pickup pattern and transducer type. |
| Pickup Patterns | Sensitivity to where sound information comes from; Bi-directional; Cardioid; Shotgun; Omni Directional |
| Transducer Types | The way the microphone captures vibrations; can be Dynamic or Condenser. |
| Dynamic Microphone | Uses a diaphragm and a metal coil; movement of the diaphragm creates changes in the magnetic field; creates different currents recorded as different sounds; can take a lot of abuse and handle high sound pressure. |
| Condenser Microphone | Use two metal plates, a smaller one that vibrates and a stationary one; sound waves change the distance between the plates; converted to electrical energy; more sensitive and expensive; more accurate sound reproduction; require additional power. |
| Recording | Many takes and edit later; clean after you mess up; write down goals; tell people how you want them to say things; record ambient background sounds by themselves; pay attention to background noise; listen right after recording to see if it requires additional takes, especially when recording video. |
