Here are some common sounds made by Norway rats.

A note about spectograms: A spectogram is a visualization of a sound. Along the horizontal axis is time, and the vertical axis is frequency, or pitch, which is measured in Hertz (Hz). The intensity, or loudness, of a sound corresponds to the darkness of the spectogram at that point. Cornell has a more detailed explanation of spectograms. I have included spectograms of each sound below. Spectograms are used a lot in studies of animal communication (for more, go to the Cornell Lab of Ornithology or the Borror Lab of Bioacoustics).

So, a wolf-whistle sound (play sound). has this spectogram: (click on the thumbnail to get a bigger picture). In the table below, click on the thumbnail below each sound to view its sonogram.

Note: you may need to turn your volume up very high to hear these soft vocalizations. External speakers may also help.

Vocalization	Exemplar	Longer example
Peep Duration: 0.1 sec Features: high-pitched note that usually sweeps steeply upward in pitch (e.g. dominant frequency rises from 2.2 to 4.3 kHz). Sounds like a soft "bwip." Context: heard during head and body grooming.	Play Sound (56K) Snip peeps while Cricket grooms his head.	Play Sound (452K) Snip peeps several times in a row while Cricket grooms his head.
Short Squeak Duration: 0.2 sec, about twice as long as the peep. Features: high pitched note that sweeps only slightly upward or downward. Context: during head grooming, mild social interactions, and agonistic encounters.	Play Sound (64K) Short squeak by Snip during head grooming.	Play Sound (136K) Cricket and Snip are both in a tube hammock, and one of them squeaks twice.
More short squeaks...	Play Sound (44K) Widget gives "chevron-shaped" squeak during altercation with Snip.	Play Sound (156K) Widget squeaks during altercation with Snip
Chirrup Duration: 0.2 sec Features: High pitched double note, like a two-syllable double chirp, or a broken short squeak. Context: this example was heard during head and body grooming.	Play Sound (64K) Squeak chirrups while Cricket grooms his head.
Squeak-Churr Duration: 0.2 sec Features: Squeak mixed with a broad-band vocalization that sounds like a soft "churr." Churr may occur at the beginning, middle or end of the squeak. Context: heard during head and body grooming, and agonistic encounters.	Play Sound (60K) Snip squeak-churrs during grooming by Cricket	Play Sound (56K) Snip squeak-churrs during altercation with Widget
Long Squeak Duration: 0.2-0.3 sec Features: louder, high-pitched squeak (dominant frequency is around 2.5 kHz), that stays relatively constant. Context: given by subordinate rat during belly-grooming, during other tense encounters, or in strong protest.	Play Sound (72K) Snip long squeak	Play Sound (332K) Several long squeaks in a row by Snip
		Play Sound (188K) Three long squeaks by Snip during intense altercation with Widget
Broken Long Squeak Similar to the long squeak, but broken into two or more notes.	Play Sound (64K) Broken squeak by Snip, during grooming.
Shriek Duration: 0.2 sec. Features: Loud scream that covers many frequencies at once (called "broad band"), from 0.2-20 kHz and perhaps up into ultrasound. Context: Heard during fights, or when rat is in pain, or in strong protest.	Play Sound (52K) Double shriek by Widget, during petting when he didn't want to be petted.	Play Sound (636K) Long squeaks, broken long squeaks, squeak-churrs, then shrieks from Widget during an attempt to give him medicine orally by syringe (no, he wasn't hurt, just furious). After this, I found a food-med mixture that he ate voluntarily, which was easier on everyone!
Hiss Duration: about 0.5 sec Features: Intense open-mouthed hiss. Context: Emitted during escalated agonistic encounters when the rats are cannot escape each other (Berg 1974). The two hisses I have heard were emitted by the defending rat who had been backed into a cage corner. The hisses were too soft to register on my microphone, however.
Brux Duration: may last several minutes! Features: Soft, repetitive grinding of the incisors against each other. Context: Given during times of relaxation, while rat is alone or sometimes while being gently stroked. More rarely, during stress and uncertainty.	Play Sound (440K) Short sequence of Cricket bruxing	30 sec sequence of Cricket bruxing. (2.2MB) 30 sec sequence of Snip bruxing. (1.8MB) Bruxing sequence (1.0 MB). Bruxing by rat named Celia. Reproduced here with the kind permission of Angelrats of Rat Tales.
Chatter Similar to the brux, but louder and with more sharp cracking sounds. Context: usually heard during highly stressful agonistic encounters, by either the attacker, the defender, or both.	Play Sound (184K) Widget chatters during agonistic encounter with Snip	Longer sequence of Widget chattering (652K)   Longer sequence of Widget chattering, with simultaneous ultrasonic vocalizations by Snip (436K) Snip's USVs in (2) are the faint horizontal lines at the very top of the image
Distress Ultrasonic Vocalization Duration: Features: 20 kHz long squeak. This frequency is at the limits of my microphone, so it barely registers. These USVs were emitted by the subordinate rat during an intense agonistic nose-off.	Snip emits series of USVs during intense nose-off with Widget. USVs are the faint horizontal lines along top edge of sonogram, just above 20 kHz. inaudible to human ears
More sounds to come as I am able to record them!

Materials and methods: To record these sounds, I used a digital microphone (Labtec Verse 704) set up near the cage. The microphone's recording range is 100 Hz - 16 kHz, and its sensitivity is: -67 dBV/uBar, -47 dBV/uBar +/-4 db. The recordings have a 44 kHz sample rate, a 16 bit audio sample size, and there is just one channel (mono). Recordings were made less than 5 feet away from the rats, with the distance varying from a few inches to several feet.

I recorded directly into a computer. I used AudioX for the Mac OS X, a recording program, to record some of the sounds, then switched to SpectraPLUS for the PC, a signal analysis program, to record more sounds and create spectrograms. Lastly, I used Felt Tip Sound Studio for the Mac to increase the volume and reduce some of the low frequency noise on the softer sounds (peeps and short squeaks).

Here are Cricket and Snip getting ready to record. Later, here is Cricket bruxing into the microphone.