High pitched tone comes on whenever radio is turn on

I have a 1994 Acura Legend that I bought used....appears to have the factory installed radio and car alarm. Last winter, whenever it was very cold, a high pitched tone (could be the alarm) would sound whenever the radio was turned on. The radio could be heard below the high pitched tone. Turning off the radio would silence the tone. After the car warmed up, the radio could be turned back on and the tone would be gone. Recently, temperature appears to be no longer a factor as it has been hot outside and the tone now is present whenever the radio is turned on... irregardless of the car's temperature. I do not have a factory manual for the car.
What should I do to silence the tone and again enjoy the sounds of the radio?