Sennheiser MX W1 Instruction Manual page 23

Problem
Humming
noise
Only one
earphone has
audio
Earphones
cannot be
switched on
Resetting the transmitter to the factory settings
If a problem occurs that is not listed in the above table or if the
problem cannot be solved with the proposed solutions, please
contact your local Sennheiser agent for assistance.
Possible cause
Interference when
charging from the PC
Transmitter was
switched on before the
earphones were
switched on
Rechargeable batteries
have just been replaced
In case of system malfunction:
Use a pointed tool to press the reset button
for 1 second.
The transmitter is reset to the factory
settings and then restarted.
Possible solution
Charge from the
power supply unit or
choose a different
audio source
Briefly press the
transmitter's
operation/pairing
button
Briefly charge the
earphones
(see page 18)
21