Sound (medical instrument)
In medicine, a sound (), also called a sonde (), is an instrument for probing and dilating passages within the body, the best-known examples of which are urethral sounds and uterine sounds. == Urethral sounds == Urethral inserted into the male or female urethra, for the purpose of stretching or unblocking a stricture.
Source: Wikipedia — Sound (medical instrument) (CC BY-SA 4.0)