The chamber was virtually soundproof, so the only way for occupants to signal unhappiness or distress was to tap insistently on the chamber wall or to hold up notes to a small window.
The flats had had a makeover – the balconies were now sealed with airtight windows that presumably made the flats warmer and more soundproof, but which further separated the residents from the natural world.
In the 1970s, the activity became recreational, with soundproof, lightproof flotation tanks that keep you buoyant with salt water that is the same temperature as your body.