Cat Sound Localization: 10 Microseconds, 7 cm

A cat can place a mouse rustle to within about 7 cm at 1 m, in near darkness, without moving its eyes. The trick rests on 2 signals: a 10 microsecond difference in arrival time between the two ears, and a set of spectral notches carved by the shape of the pinna. Both are cheap in energy, expensive in wiring, and both degrade under the same 3 conditions — background noise, a blocked canal, and age.

Ten microseconds is a 3.4 mm head start

Sound covers 343 m at 20 C, so a 10 microsecond arrival gap equals 3.4 mm of extra path, less than a grain of rice. On a head 6 cm wide the maximum gap at 90 degrees is about 225 microseconds; at 30 degrees it is already 90, and at 15 degrees 46. The brainstem compares the two spike trains through coincidence detectors that fire only when both inputs land within a few tens of microseconds. Behavioral work puts the cat's discrimination threshold near 10 microseconds, which asks the wiring to resolve a difference of about 1/100,000 of a second — the kind of number that explains why the auditory pathway takes up so much brainstem space in a carnivore that hunts by ear.

Two steerable dishes, about 32 muscles each

The pinna is not a fixed funnel. Each ear carries on the order of 32 muscles and swivels through roughly 180 degrees, and the two ears move independently, so they can aim 30 to 40 degrees apart. A cat tracking a sound turns its head first, in 0.2 to 0.3 seconds, then fine-tunes with the ears. The cone, 2.5 to 4 cm deep, behaves like a horn: 5 to 10 dB of gain between 4 and 10 kHz, exactly the band where a mouse squeak and a kitten distress call sit. Its ridges and notches also stamp a direction-dependent dip of 1 to 2 dB between 8 and 12 kHz, and that dip is the only cue that survives when the two ears agree. Pinna shape varies by breed: a folded or curled ear loses part of that notch, and at close range the whiskers take over part of the job.

Left and right by timing, up and down by shape

Azimuth is solved by time and level. Elevation cannot be: a source 20 degrees above the horizon and one 20 degrees below produce nearly identical interaural differences, so the cat reads height from where the spectral notch falls. That asymmetry shows up in the error: horizontal localization is good to about 7 cm at 1 m, roughly 4 degrees, while vertical error runs 1.5 to 2 times larger. A cat facing a sound it cannot place tilts and rotates its head 2 or 3 times, changing the notch position until the two readings agree.

Angles, timing, and error at 1 m

Source angle	Interaural time	Level difference	Error at 1 m
0 degrees	0 microseconds	0 dB	about 12 cm
15 degrees	46 microseconds	1 to 2 dB	about 8 cm
30 degrees	90 microseconds	3 to 4 dB	about 7 cm
60 degrees	167 microseconds	8 to 10 dB	9 to 12 cm
90 degrees	225 microseconds	15 to 20 dB	12 to 15 cm

The 0 degree row surprises people: dead ahead is the hardest angle, because both ears receive the same signal and the only cue left is the spectral one. That is why a cat hunting a sound directly in front moves its head a few centimetres rather than staring harder.

What noise does to the 7 cm number

Localization is a comparison, so anything that adds jitter to the two inputs costs accuracy. At a signal-to-noise ratio near 0 dB, error in cats roughly doubles to triples, and 7 cm becomes 15 to 20 cm at 1 m. Above about 65 dB of broadband noise — a vacuum cleaner at 1 m runs 70 to 80 dB — the strategy changes: instead of one clean fix, the cat scans with head sweeps of 15 to 30 degrees at 1 or 2 per second. Two practical consequences. Calling a cat from across a noisy kitchen gets a blank stare, while calling from a doorway 2 m away works. And a cat that stops responding to its name in a room with a running extractor fan is not losing its hearing.

Distance is a separate calculation

Level differences only carry distance information above about 2 kHz, where a 6 cm head casts a real shadow: at 8 kHz the wavelength is 4.3 cm and the far ear gets 10 to 20 dB less. Below 1 kHz, wavelength 34 cm, sound bends around the head and level cues disappear. For distance, cats fall back on loudness, reverberation, and echo delay — a source 1 m further away adds 5.8 ms of echo time, and 2 m adds 11.6. This is why a cat can walk straight to a container it has never seen, but misjudges a sound behind a closed door by 30 to 50 cm.

Old ears lose the top octaves first

The cat's range runs 48 Hz to 64 kHz, about 11 octaves, against 10 for a human at 20 Hz to 20 kHz. Age-related loss starts at the top: by 14 years many cats have little response above 16 to 20 kHz, which is the band a bag of treats and a crinkle toy occupy. A cat that no longer lifts its head for a key jingle at 3 m, but turns for a hand clap, has a high-frequency loss, not stubbornness. Test it 3 times from 2 m behind the cat, out of sight, and if the ear does not flick on any of them, ask the vet about a hearing check rather than shouting louder.

Ear signs that need a vet

Book a visit for a head tilt over 15 degrees that lasts more than 24 hours, eyes flicking side to side, a soft swelling on the pinna that fills within a day, discharge or a smell from one ear, or scratching at one ear more than 5 times an hour. A cat that suddenly walks in circles or vomits with the tilt has a vestibular problem, and middle-ear disease in cats often hides behind what looks like a mild ear infection. Untreated, the hearing loss that follows is permanent, and the localization skill described above does not come back.

Four things the numbers change at home

1. Call the cat from a doorway, not from across a noisy room, and stay still while it searches: a moving caller adds a second error.
2. Keep sound toys under 80 dB at 30 cm; some crinkle and squeak toys hit 90 to 100 dB at 10 cm, which is louder than the cat needs.
3. Rattle a container at 2 m rather than 5: beyond 3 m, indoor echoes cost the cat 20 to 30 cm of accuracy.
4. Check both ears monthly for wax, smell, and symmetry, and treat a 1 day old pinna swelling as urgent — a hematoma left 48 hours shrinks the ear canal.

Terms mentioned in this article

MM

Frequently asked