More than 150,000 people have checked their hearing via a telephone test, a charity says.
The hearing test takes five minutes by telephone
RNID launched its Breaking the Sound Barrier Campaign with an advert on Christmas Day - attracting on average 5,500 calls a day to the phone number.
It aims to target the 4 million people in the UK who could benefit from wearing a hearing aid but are not doing anything about it.
The test, on 0845 600 55 55, takes five minutes, with responses via the keypad.
More than 40% of over-50s are estimated to experience some level of hearing loss, the charity said.
The campaign is supported by the TUC, which wants to encourage the UK's 28 million workers to take the test.