WHAT IS AN ACOUSTICS?

• Acoustics is the study of airborne sound and structural vibration propagation over the frequency range to 2 to 20 Khz.
• Decibel- the unit used to qualify the level of sound (or loudness) to an arbitrary reference point. (Zero is equal to 20 Pa.)
• Hertz- the unit of frequency internationally accepted as 1 cycle per second.

Introduction

The plumbing system can be the source of one of the most intrusive, unwanted noises in high rise apartment buildings, hotels, hospital and dormitories. It is essential therefore that plumbing engineers understand the terminology in the field of theory of acoustics in order to reduce the acoustical impact of plumbing.

Acceptable Acoustical Level in Plumbing

*Assessed in number of ways

1. Classification of building occupancy
2. External noises from other source
3. Socio economic nature of a building (location)

*Background Sound Level

1. for broadcast studio – range from 10 to 25 decibel (db)
2. sleeping quarters – range from 20 to 35 decibels (db)
3. offices – ranges from 30 to 55 decibels (db)

Acoustical Ratings of Plumbing Fixtures and Appliances

The acoustical rating tests for fixtures are still in their infancy and have not yet been internationally standardized. United States has yet to formalize any acoustics plumbing test. The problem of adequately defining the direct airborne and structure borne of components vibration still constitute a major problem in performing acoustic rating test. Only the German standard din 52218 laboratory testing on the noise emitted by valves, fittings and appliances used in water supply installations.

Also the International Organization for Standardization (ISO). Has published standard 3822/1 laboratory test on noise emission by appliance and equipment used in water supply installation. And the American society of testing and materials (ASTM) has established a project e-33.08b the plumbing noise to investigate this problem.

• Valves – sound level depends upon the size of the fittings, the mass flow rate and the pressure differential across the fittings.
• for a well designed and properly installed fittings may range between
• 30 to 50 db.
• For adequately designed and adequately installed fittings, may range between 50 to 70 dB.
• For poorly designed and poorly installed fittings, may range between 70 to 95 dB.

WATERCLOSET– noise can be subdivided into;

• Water flushing the closet bowl.
• Water refilling the tank.
• Flush valve operation, including water discharge into the fixture and the ejection of materials from the closet bowl.
• Older style fittings with tank located as much as 6 ft. above the bowl may range between 90 to 100 dB, while modern close-coupled tanks when properly installed maybe as low as 55 dB.
• Noise of tank refilling maybe as low as 40 dB at 3 feet in a well designed unit with quiet valve.
• With poorly designed installation operating at the maximum flow rate noise maybe as high as 95 dB.
• Flush-valve operation can be as high as 95 dB.
• Blowout type fixtures have been recorded as high as 120 dB.

URINALS– The noise associated with it is the function of the wall mounting method used to install the fixture and the flushing action of the urinal, water discharge to the fixtures and the ejection of the materials. The flush valve operation maybe as high as 95 dB and Blowout unit as high as 110 dB.

BATHUBS-the noise from bathtubs i usually caused by the impact of a high velocity water stream into a glazed metallic, fiberglass, or acrylic bathtub. while the noise varrying during the filing cycle, it may also be significant during the drainage cycle. the noise of a bathtub filling typically lies in the range of 60 to 100 db(a) at 3 feet defending on the flow rate.

SHOWERS – shower noise is mostly a function of the floor surface in the shower enclosure and the type of the shower head. shower noise typically lies in the range of 60 to 90 db(a) at 3 feet.

DISHWASHER– dishwasher noise is the function of basic design of unit, the choise of the mounting procedures employed and the extent to which the installer provides additional hermal and acoustics insulation and the noise can be minimized by mounting the units rubber isolation devices or by providing layer of fiberglass insulations. typical noise range as high as 105 db(a) created by solenoid operation.

WASTE-DISPOSAL UNIT– sink or waste disposal-unit is a function of the design of the unit as well as the design of the sink or basin to which it is attached. lightly attached, stainless-steel sink or basins will tend to amplify the sound energy. Many manufacturers do not publish the noise rating data. Noise level can vary bet. 75 to 105 db(a) at 3 feet.

WASHING MACHINES

WATER PIPES

• origin and spread of noise
• reducing the noise at its origin
• reducing the spread of noise

OCCUPIED DOMESTIC SPACES PUMPS

SOURCES OF NOISE

1. unbalanced motor
2. pulsation of air mass flow from electric fans
3. pulsation of magnetic fields in the electric motor.
4. motor/gear/pump journal and thrust bearings.
5. contacting of the components in parallel shaft and epicyclic gears.
6. imbalance of the pump impellers.
7. pulsation in the pumps.
8. cavitation