We hear sounds over a frequency range that spans somewhat over 10 octaves. Our hearing sensitivity varies with frequency. Each sound has unique characteristics as to energy content in each octave. One sound at a given loudness may not be noticeable while another sound at the same loudness level may be irritating. Hearing acuity is not the same for everyone.
Sound constructions vary considerably in their sound isolation characteristics.
To help make acoustical design more manageable, various rating systems have been devised. Although single number rating systems are useful for simplifying the design process, refinements are lost. Octave or third octave band calculations should be used as a final check of a design in close or critical situations. The sound spectrums produced by five types of sound equipment that may be used in hotel guest rooms are compared in the graphs in Fig. 1. 1b shows the level in the 125 Hz octave and Fig.