Frank ICSE Solutions for Class 9 Physics - Sound: Range of Hearing PAGE NO: 284 Solution 1: The frequency of sound is defined as the number of vibrations produced by the sound producing object per second.Solution 2: S.I unit of frequency is hertz.Solution 3: One hertz is defined as one vibration produced in one second by sound producing object.Solution 4: The … [Read more...] about Frank ICSE Solutions for Class 9 Physics – Sound: Range of Hearing