| Term | Definition |
|---|
| Sound Wave | A vibrational disturbance of molecules. Sound 'works' because air is an elastic medium. |
| Compression | That part of a waveform ay which the atmosphere is compressed as a soundwave oscillates. It is the part of the waveform cycle that trajects above the center line. |
| Rarefaction | The point in a soundwave at which a partial vacuum occurs. It is the part of a waveform's cycles that falls below the center line. |
| Waveform | A graphic representation of a soundwave. |
| Simple Waveforms | Waves that are continuous and repetitive,and symmetrical about the center line. Typically a waveform that is generated electronically represents a single soundwave. |
| Complex Waveforms | Waves that do not repeat and which are not symmetrical about the center line. Typically, this is the interaction of two or more sound waves, resulting in a new waveform. |
| Amplitude | The distance above or below the center line of a waveform. |
| Center Line | That point in a waveform that represents a molecule's position with no vibrational disturbance. |
| Peak Amplitude | The positive and negative maximums of a waveform. |
| Frequency | The number of times in a second a soundwave completes one cycle |
| Cycle | The completion of a waveform from its start at the center line through one step of both compression and rarefaction, arriving back at the center line. |
| Pitch | How we perceive frequency. |
| Fundamental | Lowest frequency of a given sound. Perceived as basic pitch. |
| Hertz | The unit of frequency that is measured in cycles per second. (Hz) |
| Audible Spectrum | The range of frequencies that humans can hear, typically considered to be from 20Hz to 20KHz. |
| Midrange | The frequencies typically characterized between 320Hz and 2560Hz. Humans are the most sensitive to midrange. |
| Velocity | The speed at which a wave travels through a medium. At 70 degrees F, the speed of sound waves in air is approximately 1130 ft/sec. This speed is temperature dependent and increases at a rate of 1.1 ft/sec for each degree Fahrenheit increase of temperature. |
| Wavelength | The actual distance in the medium between the beginning and the end of a cycle. |
| Phase | The time relationship between two or more sound waves at a given point in their cycles. |
| Phase Cancellation | When soundwaves of different frequencies occur at the same time (or of the same frequency starting at different times), the interaction of compression and rarefaction results in the reduction of the amplitude of certain frequencies. |
| Harmonic Content | The factor that enables us to differentiate between instruments as the presence of several different frequencies in the sound wave, in addition to the one being played, which is called the fundamental. |
| Timbre | Describes the tonal quality of any sound, based on the mix of the fundamental and harmonic frequencies (relative amplitude). |
| Envelope | Every instrument produces its own characteristic envelope which works in combination with its timbre to determine the subjective sound of the instrument. the envelope of a waveform describes that its intensity varies and can be viewed on a graph by connecting the peak points of the same polarity over a series of cycles. Electronic: Attack, decay, sustain, release. Acoustic: Attack, sustain, decay. |
| Dynamic Range | The ratio of a sound's quietness to loudness, or lowest to highest amplitude. |
| Harmonic Frequency | Any frequency that is a multiple of the fundamental frequency. |
| Attack | The beginning of a sound or the initial transient of the wave. |
| Sustain (Internal Dynamics) | The level of the 'held' or lingering part of a note. |
| Decay | The time it takes for a sound to fade below the threshold of hearing. |
| Transient | An abrupt increase in signal level. |
| Internal Dynamics | Volume increases, decreases, and sustain after the attack of the musical note. |
| Masking | The covering of a weaker sound with a stronger sound. |
| Frequency Response Curve | A graphic representation of a device's linearity. |
| Decibel | A unit of measurement that represents sound pressure level. |
| Threshold of Hearing | The minimum sound pressure level that produces the phenomenon of hearing in most people. |
| Threshold of Feeling | The SPL that will cause discomfort in a listener 50% of the time (about 118 dB SPL between 200-10KHz). |
| Threshold of Pain | The SPL that causes pain in a listener 50% of the time (140dB SPL between 200-10KHz). |
| Harmonic Distortion | The production of waveform harmonics that do not exist in the original signal. |
| Fletcher-Munson Curves | Also known as equal loudness curves, a graph that indicates the average ear sensitivity to different frequencies at different volume levels (SPL). |
| Harmonics | Multiples of the fundamental that give an instrument its characteristic sound. |
| Beat(s) | The result of generating two tones that differ only slightly in frequency and approximately the same amplitude. |
| Sound Pressure Level (SPL) | The pressure of a sound vibration or energy measured at a specific distance from the sound source. |
| Direct Sound | A sound wave that travels a straight line and arrives at the listener's ear before hitting any other surfaces. |
| Reflected Sound | Sound waves that bounce off surrounding surfaces before reaching the listener's ear. |
| Octave | The interval between two frequencies having a ratio of 2:1. |
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