The cause of noise:
The car and FM transmitter channel overlap with your local channel rather than blank channel, so the sound quality may be blurred.So adjust to the blank channel (no broadcast).Adjust the insertion position and orientation of the FM transmitter.To prevent noise, please do not increase the volume of the car horn and use the device to increase the volume of the device.Avoid using in places where FM radio interference is strong, such as TV stations or radio stations. Avoid using in places with a lot of dust, high temperature and humidity.