In music, an octave or perfect octave is the interval between one musical pitch and another with double its frequency. The octave relationship is a natural phenomenon that has been referred to as the "basic miracle of music", the use of which is "common in most musical systems". The interval between the first and second harmonics of the harmonic series is an octave.
In music theory, a scale is any set of musical notes ordered by fundamental frequency or pitch. A scale ordered by increasing pitch is an ascending scale, and a scale ordered by decreasing pitch is a descending scale.
Absolute pitch (AP), often called perfect pitch, is a rare ability of a person to identify or re-create a given musical note without the benefit of a reference tone, it is estimated that 1 in 10,000 people (0.01%) have perfect pitch. AP may be demonstrated using linguistic labeling, associating mental imagery with the note, or sensorimotor responses. For example, an AP possessor can accurately reproduce a heard tone on a musical instrument without "hunting" for the correct pitch.
A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played with the bass pitch of the tone moving upward or downward, it is referred to as the Shepard scale. This creates the auditory illusion of a tone that seems to continually ascend or descend in pitch, yet which ultimately gets no higher or lower.
In music theory, the tritone is defined as a musical interval composed of three adjacent whole tones. For instance, the interval from F up to the B above it is a tritone as it can be decomposed into the three adjacent whole tones F–G, G–A, and A–B.
Pitch is a perceptual property of sounds that allows their ordering 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.
Auditory illusions are false perceptions of a real sound or outside stimulus. These false perceptions are the equivalent of an optical illusion: the listener hears either sounds which are not present in the stimulus, or sounds that should not be possible given the circumstance on how they were created.
A harmonic sound is said to have a missing fundamental, suppressed fundamental, or phantom fundamental when its overtones suggest a fundamental frequency but the sound lacks a component at the fundamental frequency itself. The brain perceives the pitch of a tone not only by its fundamental frequency, but also by the periodicity implied by the relationship between the higher harmonics; we may perceive the same pitch even if the fundamental frequency is missing from a tone.
The octave illusion is an auditory illusion discovered by Diana Deutsch in 1973. It is produced when two tones that are an octave apart are repeatedly played in alternation ("high-low-high-low") through stereo headphones. The same sequence is played to both ears simultaneously; however when the right ear receives the high tone, the left ear receives the low tone, and conversely. Instead of hearing two alternating pitches, most subjects instead hear a single tone that alternates between ears while at the same time its pitch alternates between high and low.
The glissando illusion is an auditory illusion, created when a sound with a fixed pitch, such as a synthesized oboe tone, is played together with a sine wave gliding up and down in pitch, and they are both switched back and forth between stereo loudspeakers. The effect is that the oboe is heard as switching between loudspeakers while the sine wave is heard as joined together seamlessly, and as moving around in space in accordance with its pitch motion. Right-handers often hear the glissando as traveling from left to right as its pitch glides from low to high, and then back from right to left as its pitch glides from high to low.
The absolute threshold of hearing (ATH) is the minimum sound level of a pure tone that an average human ear with normal hearing can hear with no other sound present. The absolute threshold relates to the sound that can just be heard by the organism. The absolute threshold is not a discrete point, and is therefore classed as the point at which a sound elicits a response a specified percentage of the time. This is also known as the auditory threshold.
Deutsch's scale illusion is an auditory illusion in which two series of unconnected notes appear to combine into a single recognisable melody, when played simultaneously into the left and right ears of a listener.
Diana Deutsch is a British-American psychologist from London, England. She's a professor of psychology at the University of California, San Diego, and is a prominent researcher on the psychology of music. Deutsch is primarily known for her discoveries in music and speech illusions. She also studies the cognitive foundation of musical grammars, which consists of the way people hold musical pitches in memory, and how people relate the sounds of music and speech to each other. In addition, she is known for her work on absolute pitch, which she has shown is far more prevalent among speakers of tonal languages. Deutsch is the author of Musical Illusions and Phantom Words: How Music and Speech Unlock Mysteries of the Brain (2019), the Psychology of Music, and also the compact discs Musical Illusions and Paradoxes (1995) and Phantom Words and Other Curiosities (2003).
Speech perception is the process by which the sounds of language are heard, interpreted, and understood. The study of speech perception is closely linked to the fields of phonology and phonetics in linguistics and cognitive psychology and perception in psychology. Research in speech perception seeks to understand how human listeners recognize speech sounds and use this information to understand spoken language. Speech perception research has applications in building computer systems that can recognize speech, in improving speech recognition for hearing- and language-impaired listeners, and in foreign-language teaching.
Illusory conjunctions are psychological effects in which participants combine features of two objects into one object. There are visual illusory conjunctions, auditory illusory conjunctions, and illusory conjunctions produced by combinations of visual and tactile stimuli. Visual illusory conjunctions are thought to occur due to a lack of visual spatial attention, which depends on fixation and the amount of time allotted to focus on an object. With a short span of time to interpret an object, blending of different aspects within a region of the visual field – like shapes and colors – can occasionally be skewed, which results in visual illusory conjunctions. For example, in a study designed by Anne Treisman and Schmidt, participants were required to view a visual presentation of numbers and shapes in different colors. Some shapes were larger than others but all shapes and numbers were evenly spaced and shown for just 200 ms. When the participants were asked to recall the shapes they reported answers such as a small green triangle instead of a small green circle. If the space between the objects is smaller, illusory conjunctions occur more often.
Psychoacoustics is the branch of psychophysics involving the scientific study of sound perception and audiology—how humans perceive various sounds. More specifically, it is the branch of science studying the psychological responses associated with sound. Psychoacoustics is an interdisciplinary field of many areas, including psychology, acoustics, electronic engineering, physics, biology, physiology, and computer science.
Pitch circularity is a fixed series of tones that are perceived to ascend or descend endlessly in pitch. It's an example of an auditory illusion.
In music cognition, melodic fission, is a phenomenon in which one line of pitches is heard as two or more separate melodic lines. This occurs when a phrase contains groups of pitches at two or more distinct registers or with two or more distinct timbres.
Interindividual differences in perception describes the effect that differences in brain structure or factors such as culture, upbringing and environment have on the perception of humans. Interindividual variability is usually regarded as a source of noise for research. However, in recent years, it has become an interesting source to study sensory mechanisms and understand human behavior. With the help of modern neuroimaging methods such as fMRI and EEG, individual differences in perception could be related to the underlying brain mechanisms. This has helped to explain differences in behavior and cognition across the population. Common methods include studying the perception of illusions, as they can effectively demonstrate how different aspects such as culture, genetics and the environment can influence human behavior.
The speech-to-song illusion is an auditory illusion discovered by Diana Deutsch in 1995. A spoken phrase is repeated several times, without altering it in any way, and without providing any context. This repetition causes the phrase to transform perceptually from speech into song.
