How does ultrasound from rats work? - briefly
Rats generate ultrasonic vocalizations by swiftly vibrating their vocal folds and modulating airflow through the larynx, producing sounds above 20 kHz. These high‑frequency calls propagate efficiently in air and serve communication, mating, and territorial functions.
How does ultrasound from rats work? - in detail
Rats emit brief, high‑frequency sounds that exceed the upper limit of human hearing. Production begins in the larynx, where rapid vibration of the vocal folds creates pressure oscillations. Subglottal pressure, generated by the diaphragm and intercostal muscles, forces air through the narrowed glottis; the resulting airflow induces a self‑sustaining oscillation of the folds at rates of 20–100 kHz. Precise timing is controlled by intrinsic laryngeal muscles, which adjust tension and adduction to modulate frequency and amplitude.
Neural control originates in the brainstem periaqueductal gray, which integrates social and environmental cues and relays commands to the nucleus ambiguus. Motor neurons innervating the laryngeal muscles coordinate the burst patterns that define each vocalization. The acoustic signal is shaped by the supralaryngeal tract; the small size of the rat’s oral cavity and nasal passages favors higher resonant frequencies, reinforcing the ultrasonic component.
Key functional aspects:
- Communication: Ultrasonic calls convey distress, aggression, mating readiness, and pup‑maternal interactions.
- Detection: The rat cochlea contains hair cells tuned to frequencies up to 80 kHz, and the auditory cortex exhibits specialized tonotopic maps for processing these signals.
- Propagation: Short wavelengths result in rapid attenuation in air, limiting transmission distance to a few meters, which reduces eavesdropping by predators.
- Measurement: High‑sensitivity microphones (≥100 kHz bandwidth) paired with fast Fourier transform analysis capture call structure, enabling quantitative study of call duration, peak frequency, and harmonic content.
The physics of the sound follows the classic myoelastic‑aerodynamic model: airflow-induced pressure differences cause the vocal folds to open, then elastic recoil closes them, creating a cycle that repeats at ultrasonic rates. Variations in subglottal pressure and tissue stiffness shift the cycle frequency, allowing the animal to produce a repertoire of calls adapted to specific social contexts.