知唔知有冇d apps (iphone or android) 可以係通話既時候播放一d預早錄好既background 聲? 好似酒樓或K-房o既聲?
I think it is not easy.
You better make the noise with another phone or mp3 yourself.
record the noise for 4~5 mins, and store it with you mp3, then you can use it when you need, press the headphone against the mic of your mobile, it should work