QIYUE FAN · PROCUREMENT DATA GUIDE

Industrial Fan Noise Data: Sound Power vs Sound Pressure

A quotation that says only “low noise” or gives an unexplained dB value is not ready for a like-for-like comparison. Ask what quantity the number represents, which fan configuration it covers and where the supporting evidence comes from. Prepare a consistent acoustic data record for the selected fan configuration.

1. Identify the quantity before comparing the number

Sound power level, Lw, describes acoustic emission from a source under a stated operating condition. Sound pressure level, Lp, describes sound at a specified position. Distance, reflections and the surrounding environment affect the latter. Both use decibels, but they are different quantities and must not be ranked as though they were interchangeable.

If one quotation reports Lw and another reports Lp, request a common reporting basis rather than applying an assumed conversion. A source rating alone does not establish the sound pressure at an operator position or property boundary. OSHA technical background.

Concept illustration 1 · Not measurement data

1 · Source: LwAcoustic emission for the stated fan duty.

2 · PropagationDistance, reflections and installation environment.

3 · Position: LpSound pressure at the defined receiver position.

Conceptual source–path–receiver map.

2. Keep weighting and frequency information visible

An A-weighted result applies frequency weighting; an octave-band record shows information across frequency bands. An overall A-weighted number does not show the full spectrum. Label the quantity as well as the weighting, for example LWA or LpA, instead of treating “dB(A)” as a complete specification.

Ask whether the supplied band values are unweighted or weighted, the band center frequencies and how the overall result was derived. Do not add band levels arithmetically. If spectral information is needed for a specialist review, mark it as requested rather than inventing missing values. ASHRAE sound and vibration terminology.

3. Align the duty and declare each configuration

For a meaningful fan comparison, align the required airflow and pressure duty before judging sound data. Record fan model, size, actual shaft speed, gas condition, drive and accessories alongside the acoustic result. Different candidates may use different sizes and RPM. Each acoustic result must correspond to its own quoted configuration and reporting boundary. A lower-speed offer is not automatically the quieter selection at the required duty. ASHRAE recommends comparing actual sound-power data at the required airflow and total pressure and obtaining frequency-band information for the specific fan. ASHRAE, Fans chapter.

Give each operating case its own row: normal production, maximum required duty and any specified reduced-speed condition. Ask the supplier which cases the evidence covers. Keep a calculated estimate distinct from a measured result, including assumptions and any stated uncertainty.

4. Define the sound path and measurement setting

Separate inlet, outlet and casing-radiated data. Also identify whether motor and drive sound is included. An inlet-only value should not be presented as a complete equipment-package result. ASHRAE’s sound-control guidance distinguishes source paths and the surrounding propagation environment. ASHRAE sound-control guidance.

For Lp, request the measurement position, distance, height, orientation, installation setting, nearby reflecting surfaces, background-noise treatment and the measurement metric/time basis. Identify open or ducted connections and installed accessories. Ask for a test-layout sketch when words alone leave the setup ambiguous.

Concept illustration 2 · Not measurement data

InletIdentify the inlet-side result and connection.

OutletIdentify the discharge-side result and connection.

CasingIdentify casing-radiated sound coverage.

Acoustic reporting scope. Record motor and drive coverage separately; compare the categories rather than adding their values.

5. Separate the silencer scope from the fan rating

A silencer in a brochure is not necessarily included in the price. Record its location, identification and commercial status: Included / Option / By others / To be confirmed. Request the proposed device’s band-based attenuation evidence, airflow-related pressure loss and flow-generated sound information. Those are separate quantities, not a single guaranteed site reduction. AMCA silencer guidance.

Assign responsibility for checking the resulting system duty, installation interfaces and final acoustic assessment. Keep access, supports and connections within the agreed package review. Do not infer a fixed dB improvement or installed-site acceptance from an accessory description.

6. Copy this acoustic RFQ record

Use one record for each quotation revision and operating case:

Equipment: tag, proposed model, size, drive and accessory list.
Duty: airflow, pressure definition, shaft RPM and gas condition.
Quantity: Lw or Lp; weighting; overall or band values.
Boundary: inlet, outlet, casing; motor and drive included or excluded.
Setting: test installation; for Lp, receiver position and distance.
Evidence: report identifier, revision, date, applicable method and edition, and represented configuration.
Data status: measured, derived, estimated, unavailable or awaiting clarification.
Treatment: silencer location and Included / Option / By others / To be confirmed status.
Acceptance: applicable project criterion, assessment location, responsible reviewer and unresolved conditions.

A named test method is not proof of product certification. If certification is requested, record the exact claim and supporting document separately. Leave unavailable fields visible; do not replace them with a catalog adjective.

Concept illustration 3 · Not measurement data

1 · Define dutyMatch the operating case.

2 · Align basisQuantity, weighting, bands and boundary.

3 · Check evidenceMethod, report, revision and data status.

4 · Resolve scopeTreatment, owner and open items.

Procurement workflow: resolve open data fields before accepting the comparison.

Roof Exhaust: Keep Product Direction Separate from Sound Evidence

For rooftop projects, distinguish the required airflow and system resistance from the acoustic acceptance criterion. The DWT-I axial roof fan and DWT-II centrifugal roof fan are different product directions, not an acoustic ranking. Request sound data for the selected configuration rather than assuming that the same model family or a low-noise description meets a nearby receiver limit.

Record roof opening and curb/interface information, connected ductwork, any proposed acoustic treatment and the receiver location. Identify who will assess sound transmission into occupied areas and the external environment. Do not treat the fan rating as a complete installed-site prediction.

Keep noise review separate from vibration troubleshooting

For abnormal mechanical vibration, use the installation-vibration guide. For commercial boundaries, use the quotation comparison guide. Neither substitutes for an acoustic report.

Send the project criterion and available sound-data sheets with the operating duty for quotation clarification. Do not enter an unsafe area or remove protection to collect readings. Any site measurements should follow the site’s approved safety arrangements and be performed by competent personnel. Final noise assessment remains a project-specific responsibility.

Clarify the sound-data requirement before quotation

Send the fan duty, project noise criterion and available supplier data. Keep missing values marked for clarification rather than assuming a pass.

Send duty and noise requirements →