This bedroom was particularly noisy. Thin walls and creaky floorboards. It seemed you could hear everything that was being said in the neighbouring rooms. So was the room acting as a resonating chamber, a sound box. It was about 4 metres long. For a stationary wave with a node at each wall, that would mean a wavelength of 8 metres. Frequency = speed of sound/wavelength = 340/8 = 43 Hz. Even for a male voice, this would be a bit low. On the other hand, 100Hz might just hit the second harmonic!
