Application of a fiber Fabry–Perot interferometer for studying the sound response of cellular structures and aqueous solutions is discussed. Aqueous suspensions of baker’s yeast and commercial natural drinking water, treated by electrolysis, were applied as models in order to mimic processes in biological tissues and liquids. The distribution of frequency intensities in the acoustic spectrograms yields evaluation of a biological system response to the external exposure. In a yeast suspension, few minutes after the sound irradiation with the frequency of 3 kHz and the sound pressure of 50 to 60 dB, we observed regular fluctuations in the output acoustic signal, with the maximal period of about 100 s. Furthermore, a sound response in the frequency range of 400 to 600 Hz maintained in signals for few minutes after the exposure. The observed results demonstrate that the proposed interferometric sensor has strong potential in biology and medicine since it is quite simple, portable, and highly sensitive device for analyses the sound response of a living system.