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Activities in KRISS
Wan-Cho Cho
2017 CCAUV
CCAUV/17-57
KRISS
1
General
Organization change
Acoustics
Vibration
Ultrasound
KRISS
2
General
CMC updates (approved at April 2017)
Peer review
Acoustics Whole previously existing items are re-approved
Ultrasound The items of ultrasonic power are newly added
Vibration Whole previously existing items of linear vibration are re-approved The items of angular vibrations are newly added
Acoustics The items for free-field microphone sensitivity for the frequency range of 1 kHz -31.5 kHz
are newly added based on the results of CCAUV.A-K4
Ultrasound The items of ultrasonic power are updated and the uncertainties are updated
Vibration The frequency ranges of items of linear vibration are extended to 0.5 Hz The items of angular vibration are updated and the uncertainties are updated
1 Sound in Air
- Diffuse-field sensitivity - Optical measurement method
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4
Introduction
Types of sound field
Pressure field Uniform pressure, only diaphragm exposed to pressure Small coupler, cross-section of plane wave duct High S/N ratio & high stability
Free field No reverberant field, SPL distribution satisfy the inverse square law Direct field + effect of sensor body (infinite rod) Representing outdoor condition
Diffuse field Uniform pressure, plane wave incidence with same
probability for every direction Representing indoor condition
Pressure field
Free field
Radom incidence (Diffuse) field
Images from http://www,gras.dk
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Introduction
Diffuse Sound Field
General definition Sound field having equal probability of energy flow in all direction and the energy density is uniform in
a volume (Jacobsen, DTU Tech. rep., 1979; Nelisse & Nicolas, JASA, 1997) Summation of infinite-equally spaced plane wave sources General characteristics High reverberation time Uniform distribution of sound pressure Spatial correlation is given by sinc function
Sound field in real life
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Introduction
Previous Works
Standard on the Diffuse Field Sensitivity Calibration No standard issued for calibrating the diffuse field sensitivity Pressure sensitivity: IEC 61094-2 (Primary), IEC 61094-5 (Comparison) Free-field sensitivity: IEC 61094-3 (Primary), IEC TS 61094-7 (Correction), IEC 61094-8 (Comparison) No ‘Calibration and Measurement Capabilities’ registered by NMI No international comparison has been conducted
Research Works on the Diffuse Field Sensitivity Calibration Reciprocity method Basic concept & formulation: Diestel, JASA, 1961 Measurement method with a scaled reverberation chamber: Barrera-Figueroa et al., JASA, 2008 Improved result using diffuser: Milhomem et al., Internoise 2016 Random Incidence method Measurement method result: Barrera-Figueroa et al., JASA, 2007
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Random Incidence Sensitivity Method
Measurement System
System Configuration Rod: Hollowed pipe, 1 m length, same outer diameter with mic, hanged by fishing line Rotator: Motor controlled with high precision (0.1 degree resolution) Measured with 5 degree step Sound source: Compression driver + Horn Data acquisition system: B&K PULSE + LAN-XI 3060 (FFT Analyzer + Generator) Distance between source and test mic.: 4 m
Test mic.
Compression driver
Rotator
Monitor microphone
DAQ (B&K LAN-XI 3060)
Gen. CH2 CH1 PC
Controller
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Random Incidence Sensitivity Method
Measurement System
System Configuration Rod: Hollowed pipe, 1 m length, same outer diameter with mic, hanged by fishing line Rotator: Motor controlled with high precision (0.1 degree resolution) Measured with 5 degree step Sound source: Compression driver + Horn Data acquisition system: B&K PULSE + LAN-XI 3060 (FFT Analyzer + Generator) Distance between source and test mic.: 4 m
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Random Incidence Sensitivity Method
Signal Processing
Gating Process Various reflection & scattering effects are included Reflection removal should be applied Applying low-pass filtering for stabilizing impulse response (Kwon & Cho, JASA, 2013) Fluctuation in 2 kHz – 5 kHz is reduced
Frequency response at frontal direction (4160.1792662)
Steady state
response Impulse response (Filtered)
iFFT
Filtered FRF LPF
Direct path IR (Filtered)
Time gating
Direct path FRF (Filtered)
FFT Inverse LPF
Direct path response
0 0.5 1 1.5 2 2.5
x 104
0
0.5
1
1.5
2
2.5
3
3.5
Frequency (Hz)
Freq
uenc
y re
spon
se
Before gatingAfter gating
Averaged measured directivity with 3 microphones
103
104
0
1
2
3
4
5
6
7
8
9
Frequency (Hz)
Dire
ctiv
ity in
dex
(dB
)
LS1, w/ gatingLS1, w/o gatingLS2, w/ gatingLS2, w/o gating
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Reciprocity Method
Measurement System
Scaled Mini Reverberation Chamber Non-paralleled walls of aluminum plates Volume: 2.8 m3 Transmission loss of door: 30~45 dB Reverberation time: MDF plate wall: 0.38 ~ 0.60 s Steel plate wall: 0.52 ~ 0.84 s
1000 10000
0.3
0.4
0.5
0.6
0.7
0.8
0.9 MDF plate wall Steel plate wall
Rebe
rver
atio
n Ti
me
(s)
Frequency (Hz)
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Reciprocity Method
Measurement System
DAQ (B&K PULSE 3560-C)
Trans. - Receiver Amp. Insert voltage switch
(B&K 5998)
PC
Output Reference
Amplifier with 20 dB Gain (B&K NEXUS)
Output Ref.
Insert voltage junction
Transmitter (B&K ZE0796)
Pre. Amp. with 20 dB gain (B&K 2673-W-001)
Small reverberation chamber (2.8 m3)
Voltage ratio measurement Same to the free-field reciprocity measurement system - Insert voltage method - Isolating the channels of transmitter and receiver to suppress cross-talk - 20 dB preamp. gain to increase S/N ratio
Acquisition process FRF with Random noise
KRISS
0 100 200 300 400 500 600 700 800 900 1000-1.5
-1
-0.5
0
0.5
1
1.5x 10
-5
Time (ms)
Impu
lse
resp
onse
12
Reciprocity Method
Signal Processing
Contribution of direct wave For the face to face configuration, contribution of
frontal direction become larger than other directions To apply the removal process Freq. step smaller than (1/RT) Hz is required
2 2.5 3 3.5 4 4.5 5-1
-0.5
0
0.5
1
1.5x 10
-5
Time (ms)
Impu
lse
resp
onse
Direct wave
Averaging process Frequency band average: 1 Hz 1/3 octave band Spatial averaging: 18 separated points (no face to face configuration)
103
104
10-1
100
101
102
Frequency (Hz)
Vol
tage
ratio
103
104
10-1
100
101
102
Frequency (Hz)
Vol
tage
ratio
103
104
10-1
100
101
102
Frequency (Hz)V
olta
ge ra
tio
Raw data Band averaged data Spatially averaged data
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Measurement Result
Results comparison
Comparison with the sensitivities in other types of sound fields Diffuse-field sensitivity estimated by the different methods are placed
in between the pressure and free-field sensitivity
1000 10000
-40
-38
-36
-34
-32
-30
-28
Sens
itivity
(dB
re. 1
V/Pa
)
Frequency (Hz)
Pressure sensitiviy Free-field sensitivity Random incidence sensitivity Diffuse field sensitivity with FFT
1000 10000
-40
-38
-36
-34
-32
-30
-28
Sens
itivity
(dB
re. 1
V/Pa
)
Frequency (Hz)
Pressure sensitiviy Free-field sensitivity Random incidence sensitivity Diffuse field sensitivity with FFT
4180.2341431 4180.2208287
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Optical method for the future primary standard
Measurement system with gated photon correlation method
System setup Feasibility test with sine-wave tube Installation of free-field measurement system Collection of measurement data and the detailed investigation are on-going
This works was conducted by collaborating with Dr. T. Koukoulas
a former principal research scientist at NPL
2 Ultrasound
- High ultrasonic power measurement
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Ultrasound
Contact point Name: Dr. Yong Tae Kim
(Head, Center for medical convergence metrology) Email: ytkim@kriss.re.kr
Recent activities Ultrasound power Development absorbing target available to RFB method up to 300 W High power measurement system construction Fabrication of high power transducers (1 MHz, 3 MHz) Pilot study for comparison with NMIJ, NIS (2 MHz – 15 MHz) Report is submitted to SCI journal. HIFU Transducer using meta-acoustic lens HIFU phantom research for histotripsy
Future Plan (2018 - ) Pilot study high power measurement comparison in APMP APMP.U-K1 RMO KC (2018)
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High ultrasonic power measurement
High power target
Requirement Echo Reduction: 50 dB (sufficient) Single layer
Characteristics of the developed target Specific Insertion Loss: 15 dB/cm 3 cm-thickness IL = 45 dB
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High ultrasonic power measurement
System configuration
300 W US-Power
Generating Part
Measuring Part
Power transducer
Power amplifiers
Step attenuator
1 MHz Power TR.
3 MHz Power TR.
1 kW Power Amp. 500 W Power Amp.
250 W Power Amp.
100 W Power Amp. Thermal voltage converters
1 V TVC 3 V TVC 5 V TVC 10 V TVC 20 V TVC 50 V TVC
Precision Balance Absorbing target Alignment stage
50 g / 0.001 mg
100 g / 0.01 mg
Automation SW
ER: 50 dB / IL: 15 dB/cm
ER: 50 dB / IL: 30 dB/cm
H. Power 50 Ohm termination
Cooling circulator
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High ultrasonic power measurement
High power measurement and water temperature problem
Water temperature continues to rise after measurement. Difficult to maintain water temperature: (21.5 ± 2.0 ) ℃ New water tank with Cooling circulator Water temperature can be controlled
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Summary
KRISS AUV Re-organization Role, activities and research area are not changed
Acoustics Diffuse-field sensitivity Optical method for the future primary standard
On-going Research Works
Ultrasound High power measurement method Related topics to HIFU
Vibration Research on the national seismic monitoring system to make it traceable to the international
metrology standard
AUV are still in KRISS!
Thank you
표준이 올라가면 생활이 즐거워 집니다!
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