Omnipresent sun or overwhelming heat, this is a sound effect that is widely used in films. I made this sound in the studio, failing to find it in nature. Maybe it's an insect? If you know more about the source of this noise, tell me. According to another anonymous visitor: The Arizona Apache Cicada is the loudest. UCS Category: ANMLInsc. Duration: 00:44.
Telephone tone when the line is busy, in France. This is a sound wave frequency of 440 Hz sinusoidal, slightly clipped. Half a second, every second. This sound is easy to loop. UCS Category: COMTelph. Duration: 00:10.