Telephone tone when the phone rings, in the United States and Canada. These are two sound waves of frequencies 440 Hz and 480 Hz sinusoidal. This sound is easy to loop. UCS Category: COMTelph. Duration: 00:30.
Several beeps of an active sonar. This is a low frequency sonar (long range but low definition). It is a triangular wave of 1030 Hz frequency easy to put in loop. In reality, a military submarine usually has passive sonar, more sonar info: en.wikipedia.org/wiki/Sonar. UCS Category: BOATSub. Duration: 00:31.
Sound atmosphere of a cave. Created on computer, with sounds from LaSonotheque: Rain, drops of water and reverberation. Easy to loop. UCS Category: AMBUndr. Duration: 01:11.