PULSE Flushes Out Toilet Noise Using Sound Quality

Sloan Flushmate is a world market leader in the design and manufacture of pressure-assisted toilet flushing systems. Its advanced technology offers high performance but uses much less water than conventional gravity toilets. A 4-channel PULSE™ system is used to optimise the sound generated by the flushing mechanism.

A World Leader in a Niche Market
Sloan Flushmate, a division of Sloan Valve Company, was established in the mid 1980s and focuses on the development and manufacture of pressure-assisted toilet flushing systems.
Sloan Flushmate's headquarters is at New Hudson, Michigan, USA. The purpose-designed facility was built three years ago and houses about 75 employees.
Sloan Flushmate is a market leader with a majority share of the world market for pressure-assisted toilet systems. This represents some 7% of the total world market for flushing toilets. Sloan Flushmate's customers include:

• Commercial and Industrial users
• Health Care
• Education
• Hotels
• Airports and Stadiums
• Ships
• Residential and Consumer

Flushmate® - How it Works
The Flushmate® vessel traps air and, as it fills with water, it uses the water supply line pressure to compress the trapped air inside. This compressed air is what forces the water into the bowl, so instead of the "pulling" or siphon action of a gravity unit, the pressure-assist unit "pushes" waste out.

Sloan Flushmate manufactures a number of pressure-assist systems for different applications. Its products either use 1.6 gallons (6 litres) or 1 gallon (4 litres) per flush. There are many environmental and practical benefits from using a pressure-assisted toilet flushing system.

Product Development
Ming Ge is Sloan Flushmate's Product Design Engineer. Ming explains, "The sound created when a toilet is flushed is an important issue for our customers. The flushing cycle of a pressure-assist system is shorter than with a conventional gravity toilet. Our aim is to minimise the sound while ensuring high-performance products that are environmentally friendly". Ming continues, "We cooperate closely with toilet bowl manufacturers and the data from our R&D investigations is widely used in making design recommendations. The bowl acts like a loudspeaker so its design is important when considering the sound generated by flushing".

PULSE
Ming says, "Quality demands from toilet manufacturers and the building industry are constantly increasing. Two years ago we decided to invest in a multi-analyzer to make sound and vibration tests. We knew of Brüel & Kjær's excellent reputation in the field of sound and vibration, and we also had some recommendations". Sloan Flushmate purchased a Brüel & Kjær 4-channel PULSE system together with a number of microphones, accelerometers and calibration equipment.

R&D Testing
Tests are made in a specially built acoustic chamber. The internal walls of the test chamber are lined with fully reflective hard surface laminate, with deadening material between the inside surface and the outside surface of each wall. A Brüel & Kjær microphone is supported on a light tripod at a constant predetermined position. When required, a Brüel & Kjær accelerometer is mounted on the water-pressure regulator to measure vibration.
Ming explains, "It only takes about 30 minutes to set up a typical test. I carefully check the position of the microphone and calibrate it using a Brüel & Kjær Type 4231 Calibrator before each test. We are interested in frequencies over a wide range and typically investigate from 100 Hz to 16 kHz".

PULSE is set in data acquisition mode, the toilet is flushed remotely and 10 seconds of data is recorded. The test is repeated four more times to ensure that the toilet's operation is stable and the average of the five tests is calculated. The peak sound pressure level is also measured and noted. Ming says, "We would typically see an A-weighted SPL of 80-83 dB. Of course, we also make benchmark tests on our competitors' products".

User-friendly
"PULSE is easy to use and we set up our own standard test template without difficulty", says Ming. For security, the test data is saved on two hard disks. Previously stored data is often recalled for comparison purposes.
We generate reports using the standard report generating function in PULSE. The data is exported, normally to Microsoft® Word, but Excel is also sometimes used. "The reporting facility is very user-friendly", says Ming.
Joseph M. Bosman is Sloan Flushmate's Chief Operating Officer. Joseph explains, "With our products, 'sound perception' is very important. The PULSE system is a high-quality product and does everything we need. We get great technical support from Brüel & Kjær - it's above and beyond the normal. PULSE has been a great investment".

The Future
"We intend to expand our test and analysis capability with PULSE and our future plans include investing in the Brüel & Kjær Sound Quality software solution. This will enable us to create a model from the previously saved test data and to analyse the various sound metrics. We can then modify the model to achieve the optimum flushing sound, and use the jury test facility to play different sounds to a listening panel and get their subjective opinions", says Joseph.
Joseph Bosman concludes, "When making design modifications to our products to optimise the sound quality, we will immediately make a new test and quickly see the effects of the changes - the aim is to get as close as possible to optimum perceived sound".