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Sound localization is a listener's ability to identify the location of origin of a detected sound or the methods in acoustical engineering to simulate the placement of an auditory cue in a virtual 3D space (see binaural recording). Acoustical engineering is the branch of engineering dealing with sound and vibration. ...
Dummy head being used for binaural recording; the second microphone is obscured. ...
There are two general methods for sound localization, binaural cues and monaural cues. Binaural means involving both ears. Most evolved auditory systems feature two ears, one on either side of the head. ...
Binaural cues
Binaural localization relies on the comparison of auditory input from two separate detectors; most evolved auditory systems feature two ears, one on each side of the head. The primary biological binaural cue is the split-second delay between the time when sound from a single source reaches the near ear and when it reaches the far ear. This is often technically referred to as the "inter-aural time difference" (ITD). ITDmax = 0.63 ms. A less biologically important binaural cue is the reduction in loudness when the sound reaches the far ear, or the "inter-aural amplitude difference" (IAD). This is also referred to as the frequency dependource and the horizontal plane through both ears), unless the two detectors are positioned at different heights in addition to being separated in the horizontal plane. In animals, however, rough elevation information is gained simply by tilting the head, provided that the sound lasts long enough to complete the movement. This explains the evolved behavior of cocking the head to one side when trying to localize a sound precisely. To get instantaneous localization in more than two dimensions from time-difference or amplitude-difference cues requires more than two detectors. The auditory system is the sensory system for the sense of hearing. ...
A human ear of a girl An ear is an organ used by an animal to detect sound waves. ...
In vertebrates, inter-aural time differences are known to be calculated in the superior olivary nucleus of the brainstem. The calculation is believed to rely on delay lines: neurons in the superior olive accept innervation from each ear with different connecting axon lengths. Some cells are more directly connected to one ear than the other, thus they are specific for a particular inter-aural time difference. Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ...
In anatomy, the olivary bodies or simply olives (Latin oliva) are a pair of prominent oval structures in the medulla oblongata, the lower portion of the brainstem. ...
The brain stem is the stalk of the brain below the cerebral hemispheres. ...
The term delay line has multiple meanings: In electronics and derivative fields such as telecommunications, a delay line is rigorously defined as a single-input-channel device, in which the output channel state at a given instant, t, is the same as the input channel state at the instant t...
Drawing by Santiago Ramón y Cajal of cells in the pigeon cerebellum. ...
An axon, or nerve fiber, is a long slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neurons cell body or soma. ...
The tiny parasitic fly Ormia ochracea has become a model organism for studying sound localization in animals too small for ITDs to be calculated in the usual way. In this animal, the tympanic membranes of opposite ears are directly connected mechanically, allowing resolution of nanosecond time differences[1] [2] and requiring a new neural coding strategy.[3] Binomial name Ormia ochracea (Bigot, 1889) Ormia ochracea is a small yellow fly, a parasite of crickets. ...
A model organism is a species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. ...
The tympanum or tympanic membrane, colloquially known as eardrum, is a thin membrane that separates the outer ear from the middle ear. ...
Monaural (filtering) cues Monaural localization mostly depends on the filtering effects of external structures. In evolved auditory systems, these external filters include the head, shoulders, torso, and outer ear or "pinna", and can be summarized as the head-related transfer function. Sounds are frequency filtered specifically depending on the angle from which they strike the various external filters. The most significant filtering cue for biological sound localization is the pinna notch, a notch filtering effect resulting from destructive interference of waves reflected from the outer ear. The frequency that is selectively notch filtered depends on the angle from which the sound strikes the outer ear. Instantaneous localization of sound source elevation in evolved systems primarily depends on the pinna notch and other head-related filtering. These monaural effects also provide azimuth information, but it is inferior to that gained from binaural cues. Juzzah is a loser Boom, Headshot Bergamin and Gerald died The pinna (Latin for feather) is the visible part of the ear that resides outside of the head. ...
HRTFs for left and right ear (expressed here as HRIRs) describe the filtering of a sound source (x(t)) before it is perceived at the left and right ears as xL(t) and xR(t), respectively. ...
A notch filter, also called a band-stop filter, sometimes a narrow band-pass filter, or T-notch filter, is an electronic filter typically used when the high frequency and the low frequency are less than 1 to 2 decades apart (that is, the high frequency is less than 10...
Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). ...
Spheres reflecting the floor and each other. ...
Basic Definition In geography, the elevation of a geographic location is its height above mean sea level (or some other fixed point). ...
In order to enhance filtering information, many animals have evolved large, specially shaped outer ears. Many also have the ability to turn the outer ear at will, which allows for better sound localization and also better sound detection. Bats and barn owls are paragons of monaural localization in the animal kingdom, and have thus become model organisms. Suborders Megachiroptera Microchiroptera See text for families. ...
Binomial name Tyto alba (Scopoli, 1769) The Barn Owl (Tyto alba) is an owl in the barn owl family Tytonidae. ...
Processing of head-related transfer functions for biological sound localization occurs in the auditory cortex. The primary auditory cortex the region of the brain which is responsible for processing of auditory (sound) information. ...
Distance cues Neither inter-aural time differences nor monaural filtering information provides good distance localization. Distance can theoretically be approximated through inter-aural amplitude differences or by comparing the relative head-related filtering in each ear: a combination of binaural and filtering information. The most direct cue to distance is sound amplitude, which decays with increasing distance. However, this is not a reliable cue, because in general it is not known how strong the sound source is. In case of familiar sounds, such as speech, there is an implicit knowledge of how strong the sound source should be, which enables a rough distance judgment to be made.
In general, humans are best at judging sound source azimuth, then elevation, and worst at judging distance. Source distance is qualitatively obvious to a human observer when a sound is extremely close (the mosquito in the ear effect), or when sound is echoed by large structures in the environment (such as walls and ceiling). Such echoes provide reasonable cues to the distance of a sound source, in particular because the strength of echoes does not depend on the distance of the source, while the strength of the sound that arrives directly from the sound source becomes weaker with distance. The ratio of direct-to-echo strength alters the quality of the sound in a way to which humans are sensitive. In this way consistent, although not very accurate, distance judgments are possible. This method fails outdoors, due to a lack of echoes. Trinomial name Homo sapiens sapiens Linnaeus, 1758 Humans, or human beings, are biologically classified as bipedal primates belonging to the mammalian species Homo sapiens (Latin for wise man or thinking man) under the family Hominidae (the great apes). ...
In audio signal processing and acoustics, an echo (plural echoes) is a reflection of sound, arriving at the listener some time after the direct sound. ...
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