| Wave | A disturbance or oscillation that travels through space or a medium, transferring energy from one point to another without permanently displacing the particles of the medium. |
| Sound Wave | A mechanical wave caused by vibrating objects, which propagates through a medium (like air) as alternating regions of compression and rarefaction. |
| Frequency Response | The quantitative measure of a system’s output magnitude and phase as a function of input frequency. |
| Magnitude Response | Amplitude (loudness) component of the frequency response, typically represented in decibels (dB). |
| Phase Response | The component of the frequency response that expresses the timing or angular relationship between the input and output signal across frequencies. |
| On-Axis Response | The frequency response measured at a 0° angle of incidence from a sound source absent of reflections. |
| Off-Axis Response | The frequency response measured at angles other than at on-axis. |
| Listening Window | The average of the frequency responses measured on-axis and at ±15° horizontally and vertically off-axis, excluding reflections. |
| Standing Wave | A vibration pattern formed when two waves of the same frequency and amplitude travel in opposite directions and interfere, producing points of constructive and destructive interference that appear stationary in space. |
| Room Mode | A specific frequency at which standing waves form in an enclosed space due to sound reflections between room boundaries, resulting in resonant peaks and nulls in the room’s frequency response. |
| Modal Behavior | Refers to how sound behaves in an enclosed space, typically at low frequencies, due to room modes. |
| Schroeder (Room Transition) Frequency | The frequency below which room reflections dominate and modal behavior is significant. |
| Steady State Measurement | A frequency response measurement that includes both direct sound and all subsequent reflections in an environment. |
| Impulse Response Windowing | A technique to isolate the direct sound in an environment’s impulse response by truncating later-arriving reflections, improving measurement accuracy at higher frequencies. |
| Head-Related-Transfer-Function (HRTF) | A function that describes how an individual’s anatomical features (ears, head, torso) affect incoming sound, typically measured as the difference between a reference signal and what is received at the eardrum or ear canal. |
| Head-And-Torso-Simulator (HATS) | A mannequin-based measurement device that simulates average human head and torso acoustics, often used for capturing HRTFs or binaural recordings. |
| Diffuse Field | An acoustic environment where sound arrives equally from all directions, resulting in a uniform energy distribution. In headphone calibration, a diffuse-field target assumes a flat frequency response under such conditions when measured with a flat omnidirectional microphone. |
| Diffuse Field HRTF | An HRTF measured or modeled under diffuse-field conditions, representing how sound from all directions is filtered by the subject’s anatomy. |
| Transducer (Audio) | A device that converts energy between electrical and acoustic domains, such as microphones (acoustic to electric) and loudspeakers (electric to acoustic). |
| Non-Linear Distortion | Distortion products, such as harmonics or intermodulation, introduced by a transducer due to nonlinear behavior. |
| Dynamic Compression | A nonlinear effect where the output of a transducer increases less than proportionally with input level. |
| Polarity | The orientation of a waveform’s positive and negative voltage (or pressure) relative to a neutral centerline. |
| Absolute Polarity | The consistent directional behavior of an audio system in response to a positive input signal—e.g., whether a positive voltage pushes a speaker cone outward. |
