Hearing

Different locations on the basilar membrane respond to different sound frequencies. Inner hair cells respond strongest at a specific frequency.

Auditory nerve fibers fire with specific timing relative to the sound wave. This timing encodes the sound's frequency.

Although individual neurons can't fire every cycle of a sine wave, populations of auditory neurons can respond with a combined response at a specific frequency.

The organization of the auditory system where different frequencies are represented by specific locations in the system (e.g., neurons with receptors for high frequencies are near others for high frequencies).

Sound intensity is represented by both the firing rate of auditory neurons and the number of active hair cells.

Larger sounds cause the basilar membrane to move over a greater area.

Different auditory neurons exhibit different frequency tuning, with some neurons having sharper tuning curves for specific frequencies.

Auditory neurons can fire at specific points (phases) in the sound wave cycle (up to ~5 kHz).

Part of the inner ear filled with perilymph.

Inner ear structure; narrow at base, wide at apex, tuned to different frequencies.

Contains hair cells that turn vibrations into neural signals.

Few hair cells, crucial for auditory transduction.

Many hair cells that amplify and sharpen inner hair cell signals.

Hair-like extensions on hair cells; movement generates signals.

Outer hair cells' role in amplifying and sharpening sound.

Carries signals from hair cells to the brain; type 1 & 2 fibers.

A more complex shape than a sine wave, representing complex sounds composed of multiple pure tones.

A mathematical method that breaks down a complex waveform into its individual sine waves (pure tones), revealing their frequencies and amplitudes.

A sinusoidal (sine) wave, the simplest periodic sound wave.

A visual representation showing the amplitudes of all the frequencies within a complex sound.

The lowest frequency component in a complex waveform, which determines the perceived pitch.

A protective mechanism in the middle ear where the tensor tympani and stapedius muscles contract to reduce the amplification of loud sounds, protecting the inner ear.

The spiral-shaped fluid-filled part of the inner ear, that converts sound vibrations into neural signals.

Changes in air pressure caused by vibrations. These changes travel as waves.

A wave of pressure changes in air caused by a vibrating source. These waves travel outward from the source.

Compression is increased air pressure, where molecules are compressed together. Rarefaction is decreased air pressure, where molecules are spread apart. These cycles create sound waves.

A unit of measurement for frequency, which is the number of cycles of compression and rarefaction per second. A higher frequency means a faster vibration.

A unit of measurement for the intensity or loudness of a sound. Higher dB values indicate louder sounds.

A complex sound wave composed of multiple pure tones. It's more intricate than a simple sine wave.

A math technique that breaks down a complex sound wave into its individual sine waves, revealing each wave's frequency and volume.

The simplest sound wave, a smooth, repeating pattern (sine wave).

A visual display showing the strength of each frequency within a complex sound.

The lowest frequency in a complex sound that determines its perceived pitch.

Higher frequencies in a complex sound that are multiples of the fundamental frequency.

The unique quality of a sound that distinguishes it from others with the same pitch and loudness. Affected by the relative strengths of overtones.

The visible part of the ear that collects sound from the environment.

Fluid found in the tympanic canal and vestibular canal of the inner ear. It helps transmit sound vibrations.

The opening where the vestibular and tympanic canals connect, allowing perilymph to flow freely and transmit vibrations.

A membrane-covered opening in the cochlea that helps release pressure from sound vibrations traveling through the perilymph.

The basilar membrane is narrow and thick at the base and wide and thin at the apex. It is tuned to different frequencies, with high frequencies causing maximum displacement at the base and low frequencies at the apex.

The intensity of a sound wave is encoded by both the firing rate of auditory nerve fibers and the number of active hair cells. Louder sounds stimulate more hair cells, and these neurons fire more frequently.

Auditory nerve fibers can only fire so quickly. When the sound intensity is high enough, the neuron reaches its maximum firing rate, and the signal is said to be saturated. This limits how loud a sound can be encoded.

Auditory neurons fire at a specific point in the cycle of a sound wave. This phase-locking provides information about the frequency of the sound, especially for lower frequencies.

Some auditory neurons are more sensitive to a specific frequency range, meaning they have sharper tuning curves. This allows the auditory system to isolate and analyze individual frequencies within complex sounds.