Application Considerations
Q Fan Sound Data
Trane Q fans are designed to be used in any installation where a standard airfoil centrifugal fan can be used. The sound level of the Q fan in the difficult to attenuate lower frequencies is lower than that produced by standard airfoil centrifugal fans with the same capacity. Sound levels in the higher octave bands compare favorably.Therefore, the Q fan will provide quieter sound levels in a typical installation.
Designing the system for lower static pressures and selecting the fan at high efficiency will result in quieter fan operation, as well as power savings.
The best method of acoustical design makes use of unit sound power levels in all eight octave bands. These sound power levels for eachTrane Q fan can be obtained from theTrane computerized fan selection program.
In the past, it has been an industry practice to test air moving devices within a reverberating room to determine total sound power.This has presented the problem of distinguishing between inlet and discharge sound power ratings, where significant differences do exist.
Trane engineers solved this problem by locating the fan adjacent to the reverberating room and ducting to it. By turning the fan around, inlet and discharge sound power can be measured separately and accurately.
By ducting both the inlet and outlet, radiated shell sound power was determined. Using this method with theTrane reverberant room that
Trane Acoustics Program
Trane has a system level acoustics computer program that accurately converts fan sound power to room NC levels. This program uses ASHRAE approved algorithms and is the most complete and accurate sound predictive program in the HVAC industry. Use of theTrane acoustics program allows all sound paths to be checked and attenuated to achieve the desired room sound levels without costly overdesigning. Contact yourTrane sales engineer for more details on this Customer Direct Service (C.D.S.) Network program.
Q Fan/Super Q II Plus Silencers Trane has a unique silencer for the Q fan. This low turbulence, high attenuation silencer dramatically reduces airborne noise from the
Trane’s Plus silencer has a field repositionable bullet (center body) that can be relocated close to the Q Fan outlet. This unique feature eliminates low frequency turbulence and makes the Q fan quieter than plug fans or other axial or mixed flow fans. Pressure drop through the Plus silencer is
Table
Plus silencer attenuation is shown in Tables
Trane ASA10B Sound Analyzer Trane offers a low cost 10 octave band sound analyzer for sound measurements. Capable of measuring noise from 30 to 123 db sound pressure with flat, dbA and dbC sound LCb weightings this rugged meter permits comparative and absolute sound measurements to be taken.
Ideas On How To Use The ASA10B The ASA10B can be used on existing jobs to measure equipment sound levels by octave bands. Compare this data with NC charts to determine what frequencies need to be attenuated and by how much. The type and cost of noise control options is a function of the problem frequency and amplitude.
On acoustical retrofits, the ASA10B can accurately compare before and after noise levels. Real measurements establish the benefit of the retrofit.
conforms to ASHRAE standards, acoustical data on the Q fan is substantially more accurate than fan ratings made using conventional techniques.Tests covered all sizes and speeds over the entire performance range of the line. A computer program was then used to determine the precise relationship of speed, size, point of operation and frequency.
DB Addition For Vane Position Indicated
Octave | Mid- | Wide | 75% | 50% | 25% |
Band | Frequency | Open | W/Open | W/Open | W/Open |
1 | 63 | +4 | +8 | +12 | +14 |
2 | 125 | +8 | +9 | +9 | +10 |
3 | 200 | +7 | +8 | +9 | +9 |
4 | 500 | +4 | +5 | +6 | +6 |
5 | 1,000 | 0 | 0 | 0 | 0 |
6 | 2,000 | 0 | 0 | 0 | 0 |
7 | 4,000 | 0 | 0 | 0 | 0 |
8 | 8,000 | 0 | 0 | 0 | 0 |
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