439a2533-8f8c-4168-b4dd-dd5df8f0f681
prompter
what is a "screeching noise"
38ea8560-1358-4f3b-bde6-f7e42a37af0f
439a2533-8f8c-4168-b4dd-dd5df8f0f681
assistant
Screeching noise is an unpleasant noise created usually when two hard surfaces rub against each other. A common example is a sound of fingernails on a black board.
28a4d143-a12b-4bb6-9537-1511f1f11c5d
38ea8560-1358-4f3b-bde6-f7e42a37af0f
prompter
By that definition, dragging a brick on pavement would make a screeching noise, but it doesn't. Are there any more requirements to create a screeching noise?
11e95510-ee3b-4b19-89ca-0cb48badb74e
28a4d143-a12b-4bb6-9537-1511f1f11c5d
assistant
The velocity of sound waves when conducted by a material varies according to the density and stiffness of the material. Concrete is a porous material that absorbs more energy from contact and has a lower frequency response, while the porcelain enameled steel used in chalkboards is far more dense and inelastic which emits stronger sound waves at a higher frequency during contact.