* The noise generated from the densely built apartment house is transmitted to the adjacent generation as well as the noise generation households and, as most of the equipment pipes of the apartment house pass through the floor slab and pass over the lower ceiling, which is called layered piping method, through the toilet pipes passing through the upper and lower floors, the sound of speech and sanitary appliances is transmitted to the adjacent toilets.
* Toilets are less affected by external noises such as traffic noises, so background noise is as low as about 25dB(A) and, as the ceiling and walls of the bathrooms are finished with reflective material and so sounds are ringing, even the small sounds that occur in the bathroom tend to be easily recognized.
* As a result of survey conducted on 131 residents of apartment houses to determine which room is felt noise best, the living room occupying the widest area in the household was the highest with 42%, and the bathroom was the second highest with 25%, so it is urgent to develop a facility for noise reduction in the bathroom.
2. Current status
Current restroom status
* In recent years, the image of toilets has changed dramatically as living facilities, and consumers' demands are changing greatly from function-oriented to environment-oriented.
- It is required to have comfort, low energy, low echo, CO₂ reduction, cleanliness, sanitation, low flushing noise, low odor, easy maintenance, no clogging, aesthetic, and universal design, so comprehensive system design reflecting such user requirements is becoming important in the design of toilet flushing devices.