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In modern high-rise buildings, elevator noise has become a core pain point in the living environment. Due to its unique coupling characteristics of low-frequency solid-borne sound and high-frequency aerodynamic noise , traditional single noise reduction methods often yield minimal results. This article will systematically analyze the technological evolution path of elevator noise control, combining cutting-edge engineering practices to reveal the paradigm shift from passive defense to active control.
Elevator noise reduction is a challenging problem in architectural acoustics, as its noise exhibits characteristics of both low-frequency solid-borne sound and aerodynamic noise. The following is a systematic analysis of noise reduction measures and technical difficulties, combined with the latest engineering practice data:
I. Elevator Noise Source Analysis and Noise Reduction Measures
1. Noise control in computer rooms (accounting for over 60% of the problem sources)
Noise type, noise reduction measures, technical parameters and effects
Traction machine vibration composite damping platform:
- 8 sets of spring dampers + rubber base
- The inert block mass is ≥1.5 times the equipment's gravity vibration transmission rate is ≤5%.
Z-weighted vibration level ≤70dB
Electromagnetic noise control cabinet with confinement layer damping material attached inside the cabinet
(3mm butyl rubber + 2mm aluminum plate) 12dB noise reduction from 100-800Hz
Ventilation and airflow noise reduction duct: micro-perforated plate + ultra-fine glass wool
(Length ≥ 1.2m) Mid-to-high frequency noise reduction ≥ 25dB
2. Shaftway acoustic control
Guide rail vibration damping bracket:
The use of a triaxial elastic support (X/Y/Z axis stiffness ratio 3:2:1) attenuates the 63Hz vibration by 15dB.
Shaft sound-absorbing layer:
Lay 50mm gradient sound-absorbing cotton (low-frequency α=0.85), in conjunction with perforated FC board.
Steel cable vibration isolation sheathing:
The cable surface is wrapped with silicone-aramid composite damping tape to reduce vibration radiation.
3. Noise reduction in the car and at the landings
Noise Reduction Principles of Partial Measures
Floating floor above the car: 5mm EPDM + 20mm gypsum board, impact noise reduction ΔLw = 18dB
The car door features a double magnetic sealing strip and a flow-guided door slider, reducing pneumatic noise by 8dB.
Install noise-absorbing brushes (nylon 66 + stainless steel wire) in the gap between landing doors to prevent air noise leakage from the shaft.
II. Technical Challenges and Solutions
Challenge 1: Low-frequency solid-borne sound transmission (most difficult to control)
The essence of the problem:
The 6.3-50Hz vibration of the traction machine is transmitted through the building structure, creating secondary radiation on the far-end walls.
Typical Case:
Vibration in the top-floor machine room of a 31-story residential building caused a 37Hz buzzing sound (measured at 42dB) in a bedroom on the 15th floor.
Innovative solutions:
Mass-tuned damper (TMD): A damping mass block (mass of 1.5% of the floor slab) is suspended under the computer room floor slab to counteract vibrations at a specific frequency.
Waveguide blocking technology: Pre-embed EPDM sound insulation sheets (thickness ≥10mm) in the shear wall of the shaft to cut off the sound bridge.
Challenge 2: Shaft cavity resonance
Formation mechanism:
The hoistway forms a Helmholtz resonant cavity (typical frequency 80-125Hz), amplifying the noise of the car operation.
Comparison of governance solutions:
method
cost
Effect
defect
Traditional sound-absorbing cotton
Low
High frequencies are effective, low frequencies are ineffective.
Fire hazards
Resonant sound absorber
middle
Target frequency band noise reduction 10dB
Precise calculation of cavity dimensions is required.
Active noise control (ANC)
high
Wideband noise reduction 15dB
Poor system stability
Challenge 3: Pneumatic whistling when opening and closing doors
Conditions for generation:
When the car is running at high speed (>2.5m/s), the airflow in the door gaps separates, generating a 1-4kHz whistling sound.
Aerodynamic optimization scheme:
Car door airflow guide profile design (referencing NACA airfoil)
Variable frequency control of the gantry crane: deceleration to 0.3m/s in the final 0.5m.
III. Actual Measurement Data of Noise Reduction Engineering Effect
Case Study: Elevator Renovation of Shanghai Tower
Standard requirements before and after parameter modification
Noise level at 1m in the computer room: 82dB(A), 68dB(A), ≤75dB(A)
Noise level in the top-floor bedroom: 44 dB(A), 28 dB(A), ≤30 dB(A)
Vibration acceleration at 125Hz: 0.15m/s² 0.03m/s² ≤0.05m/s²
Core technologies: TMD damping system + wellbore resonant sound absorber (sound absorption coefficient of 0.92 at 125Hz)
IV. Solutions to Industry Pain Points
1. Space constraints for renovating existing buildings
Pain point: Sound-absorbing layer cannot be installed when the shaft width is less than 200mm.
Innovative solutions:
Spray water-based damping coating (2mm thickness, loss factor η≥0.25)
Effect: Vibration attenuation of 63-250Hz by 6-8dB
2. Noise from ultra-high-speed elevators
Pain point: Prominent aerodynamic noise at speeds ≥6m/s
Solution:
Car roof fairing (reduces wind resistance by 35%)
Micro-perforated acoustic lining for car walls (pore diameter 0.3mm, perforation rate 1.8%)
V. Selection and Implementation Recommendations
Pitfall Avoidance Guide:
Discontinue the use of mineral wool for sound absorption in shafts (due to fiber shedding and contamination) → Replace with water-repellent fiberglass wool
Vibration dampers must undergo dynamic stiffness testing (to avoid static compression failure followed by dynamic failure).
It is essential to measure the low-frequency range of 16Hz-200Hz (ordinary sound level meters may miss these frequencies).
Conclusion: Elevator noise reduction requires a comprehensive approach.
In the near term: Prioritize addressing computer room vibration (contribution rate > 60%).
Mid-term: Shaft acoustic reconstruction blocks noise propagation
Long-term: Incorporate noise reduction design into the elevator selection stage (choose low-noise models such as magnetic levitation traction machines).
The ultimate goal is to transform elevator noise from a major source of complaints into "imperceptible background noise," which requires the integration of three major technical systems: precision vibration reduction, acoustic materials, and fluid optimization.