  Quench diagnostics in superconducting accelerator magnets is essential for
understanding performance limitations and improving magnet design.
Applicability of the conventional quench diagnostics methods such as voltage
taps or quench antennas is limited for long magnets or complex winding
geometries, and alternative approaches are desirable. Here, we discuss acoustic
sensing technique for detecting mechanical vibrations in superconducting
magnets. Using LARP high-field Nb3Sn quadrupole HQ01 [1], we show how acoustic
data is connected with voltage instabilities measured simultaneously in the
magnet windings during provoked extractions and current ramps to quench.
Instrumentation and data analysis techniques for acoustic sensing are reviewed.
