Main text The key comparison CCAUV.A-K6 has been carried out under the auspices of the Consultative Committee on Acoustics, Ultrasound and Vibration (CCAUV) of the International Committee of Weights and Measures (CIPM). This comparison is concerned with primary pressure calibration of laboratory standard microphones type LS2P. The participating NMI's are HBK-DPLA (Denmark), CENAM (Mexico), GUM (Poland), INMETRO (Brazil), KRISS (Korea), LNE (France), METAS (Switzerland), NMIA (Australia), NMIJ (Japan), NMISA (South Africa), NRC (Canada), UME (Turkey) and VNIIFTRI (Russia). The role of Pilot laboratory was undertaken by LNE (France). The measurements took place between March 2019 and December 2020. Two LS2P microphones were circulated. This report includes the measurement results from the participants, information about their calibration methods, and the analysis leading to the assignment of the Key Comparison Reference Values (KCRV) and Degrees of Equivalence (DoE). To reach the main text of this paper, click on Final Report . Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/ . The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

This is the final (Draft B) report for key comparison EURAMET.AUV.A-K5 on the pressure calibration of laboratory standard microphones in the frequency range from 2 Hz to 10 kHz. Twelve national metrology institutes took part in the key comparison and the National Physical Laboratory piloted the project. Two travelling standard microphones were circulated to the participants and results in the form of regular calibration certificates were collected throughout the project. The analysis used the results for one of the microphones only and values for both sensitivity level and sensitivity phase and have been linked to the CCAUV.A K5 key comparison reference value (KCRV) via two linking laboratories (NPL and INRIM). KEY WORDS FOR SEARCH acoustics, microphones, metrology, key comparison, pressure calibration Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

New family of ear simulators has been developed and manufactured within the framework of joint research project funded by European Commission. This paper presents results of characterization measurements of three demonstrator devices from the new family of ear simulators performed at National Metrology Institute of Turkey (TÜBİTAK UME), which is the one of the partners in the project consortium. The characterization was limited by the measurements of acoustical transfer impedance of ear simulators in various configurations and determination of dependence of acoustical transfer impedance on environmental conditions. Results of the performed measurements gave basic idea about performance characteristics of the ear simulators as well as identified some shortcomings and further research to be carried out to proceed with the developed simulators for standardization work.

Sound power level of a noise source is determined by means of sound pressure level or sound intensity level measurements performed in accordance to relevant ISO standards. The determination of sound power level according to ISO 3744, 3745 and 3746 standards is used for free field or for approximated free field conditions. Kinds of measurement surfaces, enveloping the noise source, number of microphones and their positions over the measurement surface are stated in the applied ISO standard. The effects of measurement surface and number of microphone positions on the determination of sound power level were investigated theoretically. As a measurement surface; hemisphere, parallelepiped rectangular box and cylindrical surfaces were selected. Key and additional microphone positions were taken into account in the calculations as well. Sound pressure levels of a commercially available reference sound source were measured in hemi-anechoic room using FFT with 4 Hz steps and also at 1/1, 1/3, 1/12 and 1/24 octave bands for all surfaces defined in ISO 3744 and 3746 standards. Sound power level, directivity index and uncertainty contributions resulting from measurement surfaces and number of microphone positions were calculated by using data obtained in measurements. In this paper the theoretical and experimental results are presented.

This article aims to describe the characterization of the new prototype ear simulator for neonates and demonstrate its utility in clinical measurements. Experimental evaluations have been performed in order to demonstrate consistency with the theoretical model in acoustic transfer impedance. Temperature and atmospheric pressure dependency measurements have been applied for verification of the stability of the ear simulator in variable environmental conditions. Thus, the main objective of this study is to outline the benefits of the new ear simulator in audiometric measurements for neonates. Acoustic transfer impedance of the ear simulator has been determined and compared with the theoretical model, and its environmental dependence has been studied between 100 Hz and 10,000 Hz. A modified method usually applied for reciprocity calibration of microphones has been used in measurements. Comparison of the new ear simulator with the IEC 60318-4 ear simulator and a \(2\,\hbox {cm}^{3}\) coupler has been presented. The ear simulator has been used to calibrate acoustics stimuli from an audiometer (Interacoustics AD226 with Otometrics insert earphone) and two otoacoustic emission devices (Otodynamics Otoport and Interacoustics Titan). The consistency of experimental evaluations in acoustic transfer impedance with the theoretical model has been confirmed. In clinical trials, an audiometer and two otoacoustic emission devices were investigated and a smaller standard deviation of 1.0 dB, 0.8 dB and 0.7 dB at 1 kHz, 2 kHz and 4 kHz, respectively, has been achieved compared to the old \(2\,\hbox {cm}^{3}\) coupler which has a 1.5 dB, 1.8 dB and 1.9 dB standard deviations at same frequencies. Average differences and standard deviations between the two couplers (IEC 60318-4 and the universal ear simulator) are \(11.4 \pm 0.3\,\hbox {dB}\) at 1 kHz, \(11.0 \pm 0.1\,\hbox {dB}\) at 2 kHz and \(13.3 \pm 0.2\,\hbox {dB}\) at 4 kHz. These differences represent the error incurred by using an adult ear simulator for neonates applications. The new universal ear simulator designed especially for hearing assessments of neonates has been characterized and used in clinical trials. The consistency between theoretical model and experimental measurements has been approved. Clinical trials showed that a more accurate calibration of OAE and audiometers for neonates would be possible. However, further applications for different age groups and broader clinical trials should be planned. Intercomparisons between different laboratories and clinics can maintain the comparability of hearing measurements and higher impact.

An innovative family of ear simulators has been conceived for the calibration and traceability of audiometric equipment. Each device within the family has been designed for a particular key age group, covering neonates through to adults. The age-specific ear simulators are intended to improve the quality of hearing assessment measurements for all test subject age groups, and will be proposed as the next generation of standardised ear simulators for audiometric applications. The family of ear simulators shares a common design and modeling approach, and the first prototype devices for neonatal applications have been manufactured. The objectives of this study were to develop calibration methods, verify conformance to the design goals, demonstrate that the device is capable of being calibrated reliably, and show that its performance is ultimately suitable for international standardisation and eventual adoption into clinical practices. Four national measurement institutes took part in a round-robin calibration comparison and an analysis of the results showed that these objectives were achieved.

HIFU (High Intensity Focused Ultrasound) transducers are attractive tools for cancer therapy. They must be used carefully for operator and patient safety as they produce very high powers up to a few hundred watts, and characterized in many ways. The ultrasonic power of a transducer is directly proportional to the applied input electrical voltage, current and consequently electrical power. Internationally accepted methods for measurements of ultrasonic output power up to 10 W are well established in the IEC 61161 standards [1]. The same method was used for higher powers up to 150 W with an uncertainty of 4.7% for 1.1 MHz and 5.0% for 3.3 MHz in an intercomparison between national metrology institutes [8]. In this paper, input electrical power of the HIFU transducer, which is mainly converted into ultrasonic energy, was determined. 3 methods for the measurement of electrical power delivered to a reactive ultrasonic (HIFU) transducer were compared. Electrical power measurements were realized with an expanded uncertainty of 3.3 % for up to 50 W and 4.3 % for up to 100 W in the frequency range between 0.93 MHz and 3.1 MHz. Measurement devices were calibrated and verified by establishing traceability to electrical and ultrasonic standards at TÜBİTAK UME (The Scientific and Technological Research Council of Turkey, National Metrology Institute) primary laboratories. Electrical power measurement results obtained by this method were also compared with two different conventional power meters. Electrical power measurement results detailed in this paper showed an agreement with each other and conventional power meters.

We described the first results of an on-going study of absolute gravity changes after the 17 August 1999 Izmit earthquake in Marmara region. Repeated absolute gravity measurements were carried out six stations with an A10 absolute gravimeter from 2009 to 2011 in the region. A gravimetric calibration baseline (of the range of about 415 milliGal (mGal), 1 mGal=10−5 ms−2) was established in the region for the purposes of the calibration of the relative gravimeters. The absolute gravity measurements, repeated twice a year (October, June), can resolve gravity changes with a precision better than 5 microGal (μGal)/yr interval.

A new radiation force balance (RFB) system was established at Turkish National Metrology Institute (UME) Ultrasonics Laboratory for High intensity therapeutic ultrasound (HITU) power measurements. The new system is highly stable at high power levels up to 500 Watts. The measurement system consists of a Plexiglas cylindrical balance arm, target mounting scale disks, conical reflecting and absorbing targets, adjustment nuts, and a hanging wire. Both of the two sides of balance were mounted similar size and weight targets. The equilibrium of the balance arm can be adjusted with nuts on screws located at both sides of the balance arm. Transducer was mounted to bottom of water tank. Absorbers in the bottom and the near walls of the tank were used for reflecting target case. Ultrasound power was applied to one scale of the balance where the reflecting/absorbing target was mounted and corresponding force was measured on the other scale of balance where was connected to a balance with a thin wire while the thin rest standing on a support. Ultrasound power of two HITU transducers at frequencies 0.93 MHz, 1.1 MHz and 3.3 MHz were measured with conventional and new system, the values were compared and uncertainty components were assessed in this paper.

- - The traceability of the vibration measurements to SI units is maintained through the calibration of the reference transducers. Primary calibration of the reference transducers in the field of mechanical vibration and shock is performed in accordance with the international standard ISO 16063-11 [1]. In some applications beside magnitude of the transducer’s sensitivity, the knowledge of phase shift is also required. Magnitude and phase shift of the complex sensitivity of the reference transducer could be obtained by applying the sine approximation method, described in ISO 16063-11 standard. In general, this method is applied in many leading National Metrology Institutes in the world. However, experimental implementation of the method varies from one institute to another. The experimental setup constructed in Turkish National Metrology Institute for the realization of sine approximation technique and calibration results for reference standard accelerometers are presented in this paper.

Acoustical measurements play an important role in many aspects of our daily life. In order to ensure the validity of performed measurements and to provide the necessary technical basis for decision-making, the traceability to national and international standards has to be established. The milestone for the process is the well defined hierarchy of standards developed in the specific country starting from the national standards based on the definition of SI units and ending at the calibration of instruments used in on-site measurements. This hierarchy includes primary realization of standards used in acoustical metrology and their dissemination directly by the calibration of instrumentation at national metrology institutes or indirectly through a calibration services provided by secondary level laboratories. This paper describes the current status of acoustical metrology in Turkey and outlines plans for future developments.

Realization and dissemination of the unit of sound pressure in water are carried out through calibration of hydrophones and underwater acoustic transducers. Different calibration methods applicable for different frequency ranges are available for this purpose. For calibration of reference hydrophones at low frequencies air-water pistonphone has been constructed at Turkish National Metrology Institute (UME). One of the main parts of the calibration system is optical interferometer. Two different interferometer types were used for the precise displacement measurements. The hydrophone calibrations performed by using air-water pistonphone both with homodyne Michelson interferometer and diode laser based self-mixing interferometer, ECDL.

A laser pistonphone for the absolute calibration of microphones at low frequencies has been developed at UME. The motion of an electro-dynamically driven piston in a small close cavity produces a sound pressure. Accurate measurement of the piston displacement, by self-mixing interferometry, enables this sound pressure to be calculated, and consequently the pressure sensitivity of a microphone, exposed to this sound pressure, to be determined. Absolute calibrations of type LS1P and WS1P microphones have been carried out with an uncertainty of less than 0.15 dB. The performance of the laser pistonphone has been validated by comparing the measured microphone sensitivities with those obtained by the closed coupler reciprocity method.

Electrodynamic vibration exciters are widely used for different purposes. One of their important applications is usage as a vibration generating chain in absolute calibrations of vibration pick-ups. Main requirements for the vibration-generating devices are described in relevant ISO1 standard. These. requirements are the total harmonic distortion of the acceleration, transverse, bending and rocking motion, hum and noise level, and the acceleration amplitude stability. The bending, rocking and transverse accelerations are the properties that belonging entirely to the vibration exciter. Contribution of these effects to the overall calibration uncertainty is not as small as to be assumed negligible. Investigation of the motional behavior of some of the commercial electrodynamic exciters by self-mixing interferometry has been carried out at Turkish National Metrology Institute (UME). Interferometer in configuration of the external cavity diodes laser (ECDL) constructed at UME was used for the characterization of the exciters' surface displacement in the medium frequency range.

Laser pistonphone for absolute microphone calibration in low frequency range has been realized at UME. According to the operation principle of pistonphone, the motion of a piston, which is driven electro-mechanically in a closed acoustical coupler, produces a sound pressure. Accurate measurements of the piston displacement by laser interferometry enable accurate determination of the sound pressure and, as a result, the pressure sensitivity of the microphone exposed to the sound pressure inside the coupler. Homodyne Michelson interferometer with He-Ne laser was used for displacement measurements. Since the pistonphone is operating at low frequencies, the fringe-counting method was used for the signal processing. Calibrations of LS1P microphones with the uncertainty less that 0.15 dB have been performed using laser pistonphone. Other possible metrological applications of laser pistonphone are also described in the paper.

At Turkish National Metrology Institute (UME), linear acceleration unit has been realized based on laser interferometry with different signal processing techniques. Absolute calibrations of reference accelerometers are performed by using fringe-counting and minimum point method in the frequency range from 20 to 10000 Hz. Dissemination of the linear acceleration unit to the secondary levels is carried out through a comparison calibration of vibration pick-ups by "back-to-back" method. Traceability chain for calibrations of the vibration calibrations and measurements performed at UME has been described in this paper.