Symptom

Antenna signal condition

Source

Only a buzzing sound from the speakers

• There is no radio station broadcasting.

• Signals from the antenna to the audio unit are not transmitted.

• Electric noise caused by the operation of internal circuit from the audio unit itself

• Atmospheric noise

A buzzing or crunching sound and normal sound produced at the same time from the speakers

• Though signals are transmitted from the antenna to the audio unit, electrical noise from other sources is greater.

• Electrical noise caused by the operation of electrical components on the vehicle

• Electrical noise from high tension wires, transformer substation (factory), electrical feeder line (street car), or motorcycle.

A thumping sound and normal sound produced at the same time from the speakers (FM only)

• Noise occurs due to radio wave environment at specific places (e.g. in valleys between buildings). Noise varies when the vehicle itself or surrounding vehicles move. (FM only)

• Interference between direct and reflected waves of FM signals causes noise (Multipass noise).