ध्वानिक पराश्रव्य तथा कंपन मानक और इलेक्ट्राॅनिक तथा यंत्रीकरण सेल

Acoustics Ultrasonic and Vibration Standards & Electronic and Instrumentation Cell

(MEASUREMENTS, TESTING AND R&D)

 

1. Acoustics Ultrasonic and Vibration Standards

The calibration facilities available in this area are comparable with facilities of other countries. It is equipped with advanced instrumentation for measurement of sound and vibration and calibration of electro-acoustic equipments such as ‘Norsonic’ Sound Level Analyser, ‘Pimento’ Vibration Analyser, ‘Grass’ Sound Intensity Probe and specialized Reverberation and Anechoic Chambers for carrying out sound insulation and absorption studies of materials and diagnosing machinery noise.

Contact Person:

Dr. T.K Saxena

tksaxena@nplindia.org

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National Physical Laboratory has a strong base in R&D in the area of Acoustics and Ultrasonics. The calibration and other facilities available in the area are comparable with facilities in other countries. National Physical Laboratory, New Delhi, being the National Measurement Institute (NMI) of India, has the statutory obligation to establish, maintain and upgrade the national standards of measurement and calibration facilities for different parameters.

It is equipped with advanced instrumentation for measurement of sound and vibration and calibration of electro-acoustic equipments such as ‘Norsonic’ Sound Level Analyser, ‘Pimento’ Vibration Analyser, ‘Grass’ Sound Intensity Probe and specialized Reverberation and Anechoic Chambers for carrying out sound insulation and absorption studies of materials and diagnosing machinery noise. Apex calibration and testing services and technical advisory consultancy in architectural acoustics are provided to the industry and institution of the country. R&D work is going on in applied acoustics and building acoustics.

The new facility of primary vibration calibration standard in extended frequency range of 0.1 Hz to 20 kHz had been established. The new microphone calibration standard facility using insert voltage technique was also established for the calibration of acoustic calibrators and microphones which has reduced the uncertainty in calibration to a level at par with other NMIs of APMP region.

The measurement of ultrasonic propagation parameters such as velocity and attenuation is done at the highest accuracy. NPL works on the development of measurement techniques using ultrasonics. It has, for example, already developed techniques for assessment of parallelism between faces of an opaque block, quality evaluation of ultrasonic blocks, measurement of ultrasonic velocity in membrane, attenuation measurement without invoking diffraction correction, ultrasonic C-scan of rods providing 3-D map, detection of subtle changes on surface of marble stone, theoretical modeling for determining moisture content in composite material, acoustic impedance of liquids etc.

A number of instruments have also been developed such as ultrasonic interferometer, ultrasonic immersion and contact transducers for NDT and medical applications, pellicle with 98% transmission coefficient, calibration blocks for surface wave and creeping wave probes, piezoelectric pressure transducer, ultrasonic blind aid, displacement transducer, ultrasonic atomizer, fish tag, directional hydrophone etc.

NPL maintains primary standards, viz. the standard of sound pressure, vibration amplitude and ultrasonic power. The primary standard of sound pressure (Fig. 1a) is maintained through absolute calibration of standard condenser microphones in coupler cavity by the reciprocity technique in the frequency range 31.5 Hz to 25 kHz with an expanded uncertainty of ± 0.17 dB. The primary standard of vibration amplitude (Fig. 1b) is maintained through absolute calibration of standard accelerometer by Laser interferometer technique in the frequency range 5 to 5000 Hz with accuracy better than ± 1.2 %. The primary standard of ultrasonic power (Fig. 1c) is maintained through absolute calibration of standard power transducer by electronic radiation force microbalance system in frequency range 1.0 MHz to 10 MHz and for power range from 0.01 to 10 W with accuracy better than ± 9%. The accuracy of primary standards is verified periodically through participation in Key–comparison exercises with leading NMIs in the world.

The primary standard transducers are calibrated by absolute method while secondary and measurement transducers are calibrated by comparison and transfer standard method respectively.  The accuracy of transfer standards like sound level calibrator (± 0.15 dB) and vibration level calibrator (± 1.5 %) is determined with the help of transducers calibrated by absolute methods. The working standards like measurement microphones and accelerometers are calibrated with the help of transfer standards with an overall expanded uncertainty of ± 0.3 dB for microphones and ± 2.0 % for accelerometers.

Consultancy is also provided in the setting up of the acoustic facility, noise and vibration abatement, building acoustics and for particular NDT problems.




Fig. 1a: Primary Microphone Calibration

  Standard by reciprocity technique 


Fig. 1b: Primary Vibration calibration

Standard by laser interferometry



Fig. 1c: Primary standard for ultrasonic power

measurement by radiation force balance method


Fig. 1d. Calibration of ultrasonic NDT equipment



Fig. 1e Development of artifacts for PT

in ultrasonic NDT


Fig. 1F Ultrasonic study of materials by by EMAT


The facilities available for the calibration, measurement capabilities of some parameters along with associated uncertainty are given in the following tables.

ACOUSTICS STANDARD

A. Parameters Covered

1. Sound Pressure

2. Vibration amplitude (Displacement, Velocity & Acceleration)

3. Sound Power

4. Sound Transmission Coefficient

5. Sound Absorption Coefficient

B. Facilities Available in the section (Items Calibrated)

Standards & Measurement Microphones, Sound Level Meters, Loudspeakers, Standard & Measurement Accelerometers, Vibration Meters, Tachometers, Sound Level Calibrators, Tuning Forks, Stroboscopes, Reference Sound Sources, Sound Absorbing Material, Sound Insulation Material, Crackers noise, Noise & Vibration  Measurement and Analysis

Parameters Covered Calibration Facilities available for Range and uncertainty (Expanded) at k = 2 and 95%

Sound Pressure

Standard and Measurement Microphone, Sound Level Meter, Sound Level Calibrators

 40-160 dB (20 Hz-25 kHz)

±0.05-0.17 dB

Vibrational amplitude (Displacement, Velocity, Acceleration)

Standard and Measurement Accelerometers, Vibration Meters, Accelerometer Calibrator

Displacement 0.001 – 10 mm (5 Hz-100 kHz)

Velocity: 0.01 – 1000 mm/s

Acceleration:0.10-1000 mm/s2

± 1.0 %

Sound Power

Reference Sound Sources, Miscellaneous Noise Sources

40-160 dB (31.5 Hz – 20 kHz)

±1.0 dB

Sound Transmission Coefficient (STC)

Sound Insulation Materials

± 1.0 dB (100 Hz – 4 kHz)

Sound Absorbing Coefficient (NRC)

Sound Absorbing Materials

± 5% (100 Hz – 4 kHz)

Noise and Vibration Measurement & Analysis

Fire Crackers, Multipurpose Halls, Recording Theaters, Ground Vibrations, Machinery Noise

40-160 dB(20 Hz – 25 kHz)

±1.0 dB

C. Standards Used

    1. Primary Standards

  • Primary standard of sound pressure is maintained through absolute calibration of LS1 P & LS2P    laboratory standard microphones in coupler cavity by Reciprocity Technique (IEC 61094 Part 2)
      • Primary standard of vibration amplitude is maintained through absolute calibration of laboratory standard accelerometers by Laser Interferometric technique using sine approximation method (ISO 16063-Part 11)
    • Transfer standards are used for calibration of secondary standards from Echelon II & III level Laboratories.

2. Ultrasonic Standards

CALIBRATION FACILITIES AVAILABLE FOR

* Ultrasonic Flaw Detector                   * Ultrasonic NDT Probes

* Ultrasonic Concrete Tester                * Ultrasonic Scanners   * Ultrasonic Therapy Unit

* Ultrasonic Calibration Blocks             * Ultrasonic Thickness Gauge 

PARAMETERS COVERED

Parameter

Range

Frequency

Uncertainty (Expanded)  at k=2 and 95%

Ultrasonic Pressure Ultrasonic Total Power Vibrational Amplitude Ultrasonic Velocity

50 kPa to 5 MPa

0.01 to 10 W

1.5 to 150 nm

0.5 to 1.5 MHz

0.5 to 10 MHz

0.2 to 15 MHz

1 to 20 MHz

7.5%

 9%

1 to 7.5%

0.01%

PRIMARY STANDARDS

            Radiation Force Balance

Areas of Consultancy

Institutional consultancy is offered in areas of Building Acoustics, Noise & Vibration Control, Environment Noise Pollution, Sound Reinforcement System, Environmental Impact Assessment with respect to Noise & Air Pollution, ultrasonic nondestructive testing, design of artifacts for Proficiency Testing in ultrasonics, ultrasonic study of archival materials, etc.

NPL can also help towards setting up of Calibration and Test Laboratories, Anechoic & Reverberation Chambers, Formulation of equipment selection guidelines, Training in Metrology and nondestructive testing, etc.

2. Electronics & Instrumentation Cell

This section is upgrading the existing old manual/ semi automatic systems to make them fully computer controlled unattended systems using embedded technology. If required portion or complete hardware is also designed and developed using embedded technology.

Contact Person:

Dr. T.K Saxena

tksaxena@nplindia.org

Read more

Automation and Computerization of the Instruments

Upgradation of the existing old manual/ semi automatic systems to make them fully computer controlled unattended systems using embedded technology. If required portion or complete hardware is also designed and developed using embedded technology. Development of completely new systems as per the user requirement is also undertaken. Some of the upgraded or newly developed computer controlled systems are as under:

i) Developed fully computer controlled Solid Density Standard setup.
ii) Upgraded MLW-MK70 (very old East German Bath) to fully computer controlled bath.
Developed BOD Biosens® an apparatus for quick determination of Biochemical Oxygen Demand in waste water in collaboration with CSIR-IGIB, Mall Road, University of Delhi, Delhi. US patent granted on March 15, 2011 Patent No. 7,906,008(US). Got CSIR Technology Award 2012 and Merck Millipore India Innovation Award–2012 (MMIIA-2012) for this innovation.

This technology has been transferred to M/S Forbes Marshall, A-34/35, MIDC Estate, Pimpri, Pune.

BOD Biosens® Product Launching by Vice President CSIR and Science & Technology Minister Shri. Jaipal Reddy

iv) Design and Development of high pulse field magnet system is under progress.

Custom built software as per the user requirements are also developed. Some of the softwares developed are for image processing, color recognition, offline data analysis softwares as per user requirements which involves the numerical techniques (e.g. linear and non linear regression, partial differential equations, etc.), soft computing techniques inspired by nature e.g. Neural Networks, Genetic algorithms, Ant colony optimization, particle swarm optimization techniques, etc..

Team Members:

Dr. T.K. Saxena

Chief Scientist

Dr. Mahavir Singh

Principal Scientist

Dr. PK Dubey

Senior Scientist

Mr. Naveen Garg

Scientist

Dr. Kirti Soni

Scientist

Priyanks Jain

Scientist

Mr. Gurbir Singh

PTO

Mrs. Reeta Gupta

PTO

Dr. Yudhisther Kumar

PTO

Poonam Sethi Bist

STO-1

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