<prompt> What is indicated by the term Phon?Psycho-acoustic index of loudnessNoise induced hearing lossSound spectrumOctave Band Frequency Analyzer  <response>: Noise may be expressed in psycho-acoustic terms - the phon. The phon is a psyho-acoustic index of loudness. It takes into consideration intensity and frequency. Also remember: Octave Band Frequency Analyser, which measures the noise in octave bands. The resulting plot shows the sound spectrum and indicates the characteristics of the noise, whether it is mainly high-pitched, low-pitched or of variable pitch. Ref: Parks textbook of Preventive and Social Medicine, 21stedition, page-684 