The following figure shows how the noise energy is distributed over different frequencies for three typical household appliances. The noise of the stove hood is strongest at low frequencies (125 and 250 Hz), while that of the electric drill is most intense at high frequencies (2000 and 4000 Hz). The dehumidifier noise is distributed about equally over the entire frequency range.
It would require different configurations of sound absorptive treatment to deal with these three noise spectrums.
Figure 10. Octave-band Sound Pressure Levels for three household appliances.
