Project of reducing community tonal noise incident from some chimney stacks of the biggest utility-scale power plant

1. INTRODUCTION OF
KOREAN HIGH SPEED TRAIN
2007. 7. 24

ROTEM Company
Active Noise Cancellation
System for Industrial Plants
FODS Co.
Duancan Bldg Suite #501, Achasan-ro 3, Seungdong-gu, Seoul, Korea
TEL: +82-2-6954-7956 FAX: +82-2-6954-7957
Company for Active Silencer and Noise Barrier (ANB)

2. • Chimney Noise Mitigation in Power Plants
KOEN, Korea South-East Power Co.
South Korea
Abating sound noise source of the pipes of
huge chimney in coal-fired power plants

3. • Active Noise Cancellation
 Sound noise cancelled with the interference of waveforms
 Speaker power dependent on the distance between source and speaker
 Phase-out speaker waveform exactly matched to the noise waveform
Matching the delay time
of processed sound
Noise level
Primary acoustic path
Noise
source
Noise
Recipient
Secondary acoustic path
To reduce the amplitude of noise sources : SPL(f) = H(f) * N(f); N(t) = A Cos(2*pi*f*t)
Passive barrier &
Silencer ANCvs.

4. Mitigating chimney noise in 6m-dia stack pipes
• FODS ANC System
 Reducing max 15dB of noise level under 500Hz with ten more control speakers
 Integrating multichannel ANC controllers, connected to remote site by Ethernet
Error MIC
inputs
Reference
MIC inputs
SPEAKER
Outputs
Ethernet link
Audio
CODECS
SPK power
amplifier

5. • Features of FODS’s controller
- Multichannel narrowband ANC mode
is applied to tonal noises coming from boiler, fan motor and engines
- Multichannel broadband ANC mode
is applied to white noise coming from blast and winds
- Narrowband and broadband combined ANC mode
is applied to tonal noise with some freq-band coming from construction site and industrial zone
Tonal noise
signal
Anti-phase
signal
waveform
Residual
noise
signal
Narrowband
ANC Signals
Noise reduction
Error Mic
Signal IN
Ref Mic
Signal IN
Line OUT to
Control SPK
ANC
Controller
5V DC
Power Input

6. • ANC System Components for Chimney Flue Pipes
 ANC speakers, sensor microphones, and one performance-monitoring
microphone installed in the large-diameter (6m) stack pipes

7. • ANC System Installation

8. Noise signal
SPK line out signal
215Hz
Narrowband ANC
Frequency components of SPK output
when ANC system is stable
430Hz
Multichannel
controllers are
running
Frequency components of SPK output
when ANC system is unstable
 Field testing for the output signals of installed ANC systems
• Operational Testing

9. • Performance Check for ANC System
 Checking the performance signals of installed ANC systems
ANC ON
ANC OFF

10. • Performance of ANC System
 Comparison of noise amplitudes in the cases of ANC ON/OFF
215 Hz tonal noise 430Hz tonal noises
Voltage amplitude[dB] of the performance-test TOTAL microphone for every 5 sec intervals

11. • Scope of Works for System Installation
 Installation Jobs
 Field Testing and Initial Operation
 Repair and Service Policy