Manganese complex salts of formula LMn3MnLnXM12O40m,, wherein L is 1,4,7-trimethyl-1,4,7-triazacyclononane, X is P or Si, M is Mo or W, n is 2 or 3, and m is 1 or 2, with the provisos that if X is Si, then n=2 and m=1 and if X is P, then n=3 and m=2. A noise canceller generates an offset sound for acoustically canceling the ambient sound based on a phase-inverted collected-sound electrical signal obtained when a phase of the collected-sound electrical signal is inverted and emits the generated offset sound near the sound-catching ear. The generally spherical end of the vertical support is securely received into the bore.