Pitch is a perceptual property that allows sounds to be ordered on a frequency-related scale, or more commonly, pitch is the quality that makes it possible to judge sounds as "higher" and "lower" in the sense associated with musical melodies. Pitch is a major auditory attribute of musical tones, along with duration, loudness, and timbre.
In the branch of experimental psychology focused on sense, sensation, and perception, which is called psychophysics, a just-noticeable difference or JND is the amount something must be changed in order for a difference to be noticeable, detectable at least half the time. This limen is also known as the difference limen, difference threshold, or least perceptible difference.
Robert Allan Monroe was an American radio broadcasting executive who became known for his ideas about altered states of consciousness and for founding The Monroe Institute which continues to promote those ideas. His 1971 book Journeys Out of the Body is credited with popularizing the term "out-of-body experience".
Iconic memory is the visual sensory memory register pertaining to the visual domain and a fast-decaying store of visual information. It is a component of the visual memory system which also includes visual short-term memory (VSTM) and long-term memory (LTM). Iconic memory is described as a very brief, pre-categorical, high capacity memory store. It contributes to VSTM by providing a coherent representation of our entire visual perception for a very brief period of time. Iconic memory assists in accounting for phenomena such as change blindness and continuity of experience during saccades. Iconic memory is no longer thought of as a single entity but instead, is composed of at least two distinctive components. Classic experiments including Sperling's partial report paradigm as well as modern techniques continue to provide insight into the nature of this SM store.
A mind machine uses pulsing rhythmic sound, flashing light, or a combination of these. Mind machines can induce deep states of relaxation or concentration.
Musical acoustics or music acoustics is a multidisciplinary field that combines knowledge from physics, psychophysics, organology, physiology, music theory, ethnomusicology, signal processing and instrument building, among other disciplines. As a branch of acoustics, it is concerned with researching and describing the physics of music – how sounds are employed to make music. Examples of areas of study are the function of musical instruments, the human voice, computer analysis of melody, and in the clinical use of music in music therapy.
A gamma wave or gamma rhythm is a pattern of neural oscillation in humans with a frequency between 30 and 100 Hz, the 40 Hz point being of particular interest. Gamma rhythms are correlated with large-scale brain network activity and cognitive phenomena such as working memory, attention, and perceptual grouping, and can be increased in amplitude via meditation or neurostimulation. Altered gamma activity has been observed in many mood and cognitive disorders such as Alzheimer's disease, epilepsy, and schizophrenia.
In acoustics, a beat is an interference pattern between two sounds of slightly different frequencies, perceived as a periodic variation in volume whose rate is the difference of the two frequencies.
Alpha waves, or the alpha rhythm, are neural oscillations in the frequency range of 8–12 Hz likely originating from the synchronous and coherent electrical activity of thalamic pacemaker cells in humans. Historically, they are also called "Berger's waves" after Hans Berger, who first described them when he invented the EEG in 1924.
Brainwave entrainment, also referred to as brainwave synchronization or neural entrainment, refers to the observation that brainwaves will naturally synchronize to the rhythm of periodic external stimuli, such as flickering lights, speech, music, or tactile stimuli.
Prepulse inhibition (PPI) is a neurological phenomenon in which a weaker prestimulus (prepulse) inhibits the reaction of an organism to a subsequent strong reflex-eliciting stimulus (pulse), often using the startle reflex. The stimuli are usually acoustic, but tactile stimuli and light stimuli are also used. When prepulse inhibition is high, the corresponding one-time startle response is reduced.
Music theory analyzes the pitch, timing, and structure of music. It uses mathematics to study elements of music such as tempo, chord progression, form, and meter. The attempt to structure and communicate new ways of composing and hearing music has led to musical applications of set theory, abstract algebra and number theory.
Computational auditory scene analysis (CASA) is the study of auditory scene analysis by computational means. In essence, CASA systems are "machine listening" systems that aim to separate mixtures of sound sources in the same way that human listeners do. CASA differs from the field of blind signal separation in that it is based on the mechanisms of the human auditory system, and thus uses no more than two microphone recordings of an acoustic environment. It is related to the cocktail party problem.
Dichotic pitch is a pitch heard due to binaural processing, when the brain combines two noises presented simultaneously to the ears. In other words, it cannot be heard when the sound stimulus is presented monaurally but, when it is presented binaurally a sensation of a pitch can be heard. The binaural stimulus is presented to both ears through headphones simultaneously, and is the same in several respects except for a narrow frequency band that is manipulated. The most common variation is the Huggins Pitch, which presents white-noise that only differ in the interaural phase relation over a narrow range of frequencies. For humans, this phenomenon is restricted to fundamental frequencies lower than 330 Hz and extremely low sound pressure levels. Experts investigate the effects of the dichotic pitch on the brain. For instance, there are studies that suggested it evokes activation at the lateral end of Heschl's gyrus.
I-Doser is an application for the playback of proprietary audio content. The developer claims the separately purchasable content aims to simulate specific mental states through the use of binaural beats, some of it is named after various recreational drugs. The I-Doser player has been downloaded millions of times and is based on the audio technology of a GPL-licensed binaural beat generator, SBaGen. The player can be downloaded for free, and includes some sample audio content. Additional audio content can be purchased.
Audio-visual entrainment (AVE), a subset of brainwave entrainment, uses flashes of lights and pulses of tones to guide the brain into various states of brainwave activity. AVE devices are often termed light and sound machines or mind machines. Altering brainwave activity is believed to aid in the treatment of psychological and physiological disorders.
Trance is a state of semi-consciousness in which a person is not self-aware and is either altogether unresponsive to external stimuli or is selectively responsive in following the directions of the person who has induced the trance. Trance states may occur involuntarily and unbidden.
Sniffing is a perceptually-relevant behavior, defined as the active sampling of odors through the nasal cavity for the purpose of information acquisition. This behavior, displayed by all terrestrial vertebrates, is typically identified based upon changes in respiratory frequency and/or amplitude, and is often studied in the context of odor guided behaviors and olfactory perceptual tasks. Sniffing is quantified by measuring intra-nasal pressure or flow or air or, while less accurate, through a strain gauge on the chest to measure total respiratory volume. Strategies for sniffing behavior vary depending upon the animal, with small animals displaying sniffing frequencies ranging from 4 to 12 Hz but larger animals (humans) sniffing at much lower frequencies, usually less than 2 Hz. Subserving sniffing behaviors, evidence for an "olfactomotor" circuit in the brain exists, wherein perception or expectation of an odor can trigger brain respiratory center to allow for the modulation of sniffing frequency and amplitude and thus acquisition of odor information. Sniffing is analogous to other stimulus sampling behaviors, including visual saccades, active touch, and whisker movements in small animals. Atypical sniffing has been reported in cases of neurological disorders, especially those disorders characterized by impaired motor function and olfactory perception.
Virtual hammock describes the effect of using structured sound from two isolated, stationary speakers playing into opposite ears to induce the perception of being in the presence of a single sound source which is moving back-and-forth. Rather than relying solely on a variation in sound amplitude of one speaker compared to the other, the Virtual Hammock effect utilizes a shift in phase of the sound wave of one side compared with the other. This stimulates the same physiological response in the Medial Superior Olive (MSO) portion of the brain stem—the first processing stop for auditory nerves—as is induced by an actual moving sound source. Any waveform within certain frequency bounds can be used to achieve this effect. The specific case of playing sinusoidal waves of different frequencies, which creates a continuously varying sensation of the sound source moving from side-to-side, is referred to as a binaural beat. Similarly, playing square waves of two different frequencies will create a sensation of swaying back and forth.
Vibroacoustic therapy (VAT) is a type of sound therapy that involves passing low frequency sine wave vibrations into the body via a device with embedded speakers. This therapy was developed in Norway by Olav Skille in the 1980s. The Food and Drug Administration determined that vibroacoustic devices, such as the Next Wave® PhysioAcoustic therapeutic vibrator, are "substantially equivalent" to other therapeutic vibrators, which are "intended for various uses, such as relaxing muscles and relieving minor aches and pains"; thus, vibroacoustic devices are "exempt from clinical investigations, Good Guidance Practices (GGPs), and premarket notification and approval procedures."
