Metallic

In audio, sound production: Often, the perception of a metallic sound relates to comb filtering, where the signal is slightly delayed (ms) and added to itself. Other times the perceived metallic sound is caused by high-frequency resonances. In voice recording: Typically, metallic voice occurs when increasing higher formants (F3-F4) in the voice spectrum. In singing, this is a parameter used to vary the impression of the voice.