Headphones are electroacoustic transducers worn at or near the ears that convert an electrical signal into local acoustic pressure variations. A two-channel pair can deliver different signals to the two ears. The relevant output is the sound pressure reaching the ear, which depends on the transducer, its placement and the surrounding acoustic geometry, not just the electrical input.
For a linear small-signal description, let be the input electric potential difference and the complex pressure amplitude at a specified ear location. A headphone transfer function describes both amplitude and phase. Two headphones can receive the same yet produce different ; even the same pair can produce different responses after being repositioned.[ref]
Variability in the characterization of the headphone transfer-function by Abhijit Kulkarni and H. Steven Colburn. Section I: transfer-function description from headphone input to a point in the ear canal.
Abhijit Kulkarni and H. Steven Colburn measured responses on a KEMAR acoustic mannequin with repeated placements of the headphone cushions. Placement-dependent variation complicated compensation by a fixed inverse filter. This experiment shows why a measurement needs a defined coupling arrangement: moving the device can change the acoustic system being calibrated.[ref]
Variability in the characterization of the headphone transfer-function by Abhijit Kulkarni and H. Steven Colburn. Abstract and introduction: tested supra-aural headphones, repeated placement and compensation problem.
For an illustrative amplitude example, if pressure doubles at a particular frequency while the reference pressure is unchanged, sound pressure level increases by decibels. That is a statement about pressure at the measurement point; it is not automatically a doubling of perceived loudness or a uniform change across frequencies. Headphone reproduction is therefore an electrical-to-mechanical-to-acoustic chain that must be assessed at its intended output location.
A headphone transfer function describes how an input electrical signal becomes acoustic pressure at a specified point near or within the listener's ear. For a linear small-signal description,where is complex sound pressure amplitude and the input electric potential difference. This transfer function includes both magnitude and phase. With these variables its units are pascals per volt, rather than a dimensionless gain.[ref]
Variability in the characterization of the headphone transfer-function by Abhijit Kulkarni and H. Steven Colburn. Section I: electrical input, pressure at an ear-canal point and headphone transfer.
For example, at one frequency let and apply a sinusoidal input. The pressure amplitude is under the model. A compensating filter for a desired pressure would ideally supply , but division by a small or uncertain response can demand a large, fragile correction.
The coupling to the ear is part of the system. Abhijit Kulkarni and H. Steven Colburn repeatedly positioned headphone cushions on a KEMAR acoustic mannequin and measured changes in response. Their measurements showed that repositioning could complicate compensation using a fixed inverse filter. A transfer function measured for one fitting need not remain identical after the device is moved.[ref]
Variability in the characterization of the headphone transfer-function by Abhijit Kulkarni and H. Steven Colburn. Abstract and introduction: placement-dependent supra-aural measurements and inverse compensation.
This differs from a head-related transfer function, which characterizes transformation from an external sound source to an ear location. Reproducing a desired spatial sound over headphones can require accounting for both transformations, rather than confusing the headphone's coloration with the directional effect being simulated.
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Headphones are a pair of small speakers that are worn on or over the ears, designed to provide audio output directly to the listener. They allow individuals to listen to music, podcasts, audio books, or any other sound sources without disturbing others nearby. Headphones come in various designs and types, including: 1. **Over-ear headphones**: These have large earcups that enclose the ears, providing good sound isolation and comfort for long listening sessions.