Auditory perception
ipsy | Louvain-la-Neuve
21. Schaefer resonators
Description:
* Resonators are acoustic devices that enable complex sounds to be analyzed and their specific frequencies to be identified.
* Unlike pure sound, which, like a tuning fork, has a single frequency, complex sound is made up of several different frequencies and is produced by natural or artificial sound sources.
* Schaefer's cylindrical resonators allow frequencies to be varied more finely than Hermann von Helmholtz's famous spherical resonators.
* The complete series consists of 4 tubes 60 mm in diameter.
* Each resonator consists of two brass tubes that slide into each other, and a calibrated tip.
* A scale is engraved on the inner tube.
By modifying the length, the resonator can be tuned to a specific frequency.
Operation:
* These resonators operate on the principle of acoustic resonance.
* The small end of the tube is inserted into the ear.
* When the ambient sound contains a frequency corresponding to that of the resonator, the air inside the resonator vibrates, i.e. resonates, making this frequency more perceptible.
22. Sound rhythm production device
Description:
* This device generates sound rhythms by rotating a stylus.
* At each turn, the stylus shuts a number of contacts distributed around the perimeter of a circular plate, the relative distance of which can be varied.
* Each time the circuit is closed, a condenser is discharged into a loudspeaker, which emits a short burst of sound.
* The rotation speed of the stylus is varied by means of a mechanical variator consisting of two conical elements arranged “head-to-tail” and connected by a leather belt.
* An electric motor connected to the end of the variator ensured the rotary movement of the whole device.
Operation:
* The device, created by Albert Michotte, was used to produce models of sounds that the participant had to reproduce as accurately as possible (respecting rhythm, intervals between sounds, etc.). Sound transformations were investigated.
* The technique was used by Paul Fraisse, Michotte's doctoral student at the time, as part of his thesis on rhythmic voluntary movements.
* Fraisse later became director of the Laboratory of Experimental Psychology at the Sorbonne in Paris.
23. Microphone Dralowid Reporter
Description:
* This tabletop microphone, marketed in the 1930s, features a particularly high sensitivity.
* It enables clear, unbiased reproduction of every vocal frequency.
* It is also suitable for music transmission, due to its great independence of frequencies.
* The microphone capsule is spring-suspended in order to resist mechanical shock.
* The microphone is connected to an amplifier or to a radiophonic device via a special transformer which, combined with a signalling lamp, is housed in the base.
Operation:
* In the laboratory of experimental psychology, this high-level microphone served multiple functions.
* It was used for transmitting speech and music, recording voice or sound signals, as well as for recording discs and films depicting experiments.
24. Metronome
Description:
* Most commonly used in music, the metronome emits a regular sound pulse.
* It enables the musician to play in time, but also to vary the tempo of music pieces.
* The mechanic metronome is equipped with a pendulum and is winded using a key.
* The pendulum is fitted with an adjustable weight to regulate speed.
* The lower the weight, the smaller the movements of the pendulum and the faster the tempo.
* Conversely, the higher the weight, the greater the movements, and therefore the slower the tempo.
* The metronome provides a visual movement that helps anticipate the occurrence of each beat.
Operation:
* In Michotte's laboratory, rhythm perception was investigated using complex technical devices.
* They produced series of sonic signals forming rhythmic patterns.
* Participants were exposed to these signals and their perceptual reactions were collected.
* The mechanic metronome was used as a tool for calibrating the signals generated by these devices.