Related Experiment Video
Updated: Oct 29, 2025
09:54
Morphological and Functional Evaluation of Ribbon Synapses at Specific Frequency Regions of the Mouse Cochlea
Published on: May 10, 2019
12.2K
Conversion of amplitude modulation to phase modulation in the human cochlea
Sho Otsuka1, Shigeto Furukawa2
1Center for Frontier Medical Engineering, Chiba Univ. 1-33 Yayoicho, Inageku, Chiba 263-8522, Japan; NTT Communication Science Laboratories, NTT Corporation, 3-1, Morinosato-Wakamiya, Atsugi-shi, 243-01 Japan.
Hearing Research
|July 8, 2021
Summary
Amplitude-modulation-to-phase-modulation (AM-to-PM) conversion occurs in the human cochlea, measurable via otoacoustic emissions (OAEs). This cochlear PM information may aid sound processing for some listeners.
Area of Science:
- Auditory Neuroscience
- Signal Processing
- Bioacoustics
Background:
- Amplitude-modulation-to-phase-modulation (AM-to-PM) conversion is a known distortion in electronic amplifiers.
- This phenomenon has not been previously investigated in the human auditory system.
Purpose of the Study:
- To investigate the occurrence and characteristics of AM-to-PM conversion in the human cochlea.
- To determine if the human auditory system utilizes cochlear AM-to-PM conversion for sound perception.
Main Methods:
- Recorded otoacoustic emissions (OAEs) from human subjects exposed to amplitude-modulated (AM) signals.
- Measured the phase modulation (PM) of OAEs in response to AM stimuli.
- Utilized psychoacoustic methods to estimate cochlear compression and assess AM detection performance.
- Employed a computational cochlear model to simulate observed AM-to-PM conversion.
Main Results:
- OAE phase modulation was observed, mirroring the modulation rate of the AM stimulus.
- The magnitude of AM-induced PM in OAEs peaked near the cochlear compression point.
- A computational model successfully replicated the key features of cochlear AM-induced PM.
- Psychophysical data indicated a correlation between PM sensitivity and AM detection performance in some individuals.
Conclusions:
- AM-to-PM conversion occurs within the human cochlea and can be detected using OAE measurements.
- Cochlear AM-induced PM is linked to the cochlear's nonlinear active processes.
- While not a dominant cue, AM-induced PM may contribute to sound processing for listeners with high PM sensitivity.
Related Concept Videos
01:13The Cochlea
48.0K
The cochlea is a coiled structure in the inner ear that contains hair cells—the sensory receptors of the auditory system. Sound waves are transmitted to the cochlea by small bones attached to the eardrum called the ossicles, which vibrate the oval window that leads to the inner ear. This causes fluid in the chambers of the cochlea to move, vibrating the basilar membrane.
48.0K
01:22Hair Cells
42.6K
Hair cells are the sensory receptors of the auditory system—they transduce mechanical sound waves into electrical energy that the nervous system can understand. Hair cells are located in the organ of Corti within the cochlea of the inner ear, between the basilar and tectorial membranes. The actual sensory receptors are called inner hair cells. The outer hair cells serve other functions, such as sound amplification in the cochlea, and are not discussed in detail here.
42.6K
01:15Auditory Pathway
6.1K
Auditory pathways constitute the complex neural circuits responsible for transmitting and interpreting auditory information from the peripheral auditory system to the brain. Sound waves are initially captured by the outer ear, funneled through the ear canal, and reach the tympanic membrane (eardrum). These vibrations are transmitted via the middle ear's ossicles to the inner ear's cochlea.
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking...
When viewed cross-sectionally, the cochlea reveals the scala vestibuli and scala tympani flanking...
6.1K
01:16Anatomy of the Ear
9.5K
Auditory sensation, commonly called hearing, involves the transformation of sonic waves into neural impulses facilitated by the structures of the auditory organ. The prominent, flesh-like structure on the side of the head, called the auricle, directs sound waves towards the auditory canal. The auricle is often mislabeled as the pinna, a term more aligned with mobile structures like a feline's external ear. The auditory canal penetrates the cranium via the external auditory meatus of the...
9.5K
01:31Hearing
54.5K
When we hear a sound, our nervous system is detecting sound waves—pressure waves of mechanical energy traveling through a medium. The frequency of the wave is perceived as pitch, while the amplitude is perceived as loudness.
54.5K
01:21Perceiving Loudness, Pitch, and Location
563
The human brain perceives pitch through two primary mechanisms reflected in place theory and frequency theory. Each mechanism describes how sound waves are interpreted as specific pitches by the brain, offering insights into the intricate processes of auditory perception.
Place theory, or place coding, suggests that different pitches are heard because various sound waves activate specific locations along the cochlea's basilar membrane. The brain determines the pitch of a sound by...
Place theory, or place coding, suggests that different pitches are heard because various sound waves activate specific locations along the cochlea's basilar membrane. The brain determines the pitch of a sound by...
563