The sound field in train compartments, treated as a series of connected air cavities, is modelled using statistical energy analysis, SEA. For the case under study, with five cavities in series and the source in the second cavity, a closed--form solution is obtained. An adjusted SEA model is used to predict the rate of spatial decay within a cavity. The SEA model is validated using results from a ray tracing method and from scale model measurements. For the octave bands 500-4000 Hz, good agreement is shown between the results from measurements, the ray tracing and the SEA model, for the two saloons closest to the source cavity (a vestibule). The SEA model was shown to slightly underestimate the rate of spatial decay within a cavity. It is concluded that a reasonable cause is the additional diffusion due to the seating.

A system to calibrate underwater electro-acoustic hydrophones by primary method, namely, Reciprocity method, in wide frequency range from few kilohertz to megahertz is presented. The aim is to realize primary level “Hydrophone Calibration System” covering from few kilohertz to upper limit of underwater applications with very limited restrictions in one simple system. This system not only covers wide frequency range of underwater applications but also offers low-cost solution to reach enough uncertainty level required for primary calibration according to standards [1]-[3]. The system is based on very high resolution PC oscilloscope of Pico Technology, namely, PicoScope 4262, used for primary data acquizition and digitizing. Primary signal generator and power amplifier, available in market, are integrated into system for purpose. The detailed description is presented and uncertainty budget is discussed.

Main text This report is the final report for key comparison CCAUV.W-K2. This key comparison covers primary free-field standards for sound in water at frequencies between 250 Hz and 500 kHz. This project is one of the key comparisons organised under the auspices of the Consultative Committee on Acoustics, Ultrasound and Vibration (CCAUV) of the CIPM. This report has the status of a Final Report and has been submitted to the Key Comparison Database (KCDB). In the report, the results of participants are presented with the Key Comparison Reference Values and Degrees of Equivalence. The results are calculated according to the procedures agreed after consideration of the Draft A1 and A2 reports, and the Draft B report has been approved by the CCAUV. All participants have had the opportunity to give final agreement on the contents and amendments have been made to account for their comments. In many respects, the comparison has been a success with good agreement achieved over an extended lower frequency range compared to the previous CCAUV.W-K1 comparison, the lower frequency limit for CCAUV.W-K2 being extended down by two octaves to 250 Hz. The generally more difficult frequency range from 100 kHz to 500 kHz has also shown very good agreement between the participants. However, in the range 60 kHz to 100 kHz the agreement was not as good, with three participants exhibiting some discrepant results. 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).

The project entitled “Metrology for Low Frequency Sound and Vibration” (“INFRA-AUV”), currently active within the European Metrology Programme for Innovation and Research (EMPIR). Measurement of seismic and infrasound activity is very important for monitoring natural extreme events. Low frequency sound and vibration monitoring technologies are well-established, but the sensors are often used for specific and local applications only and lack traceability. This project aims to establish both the first primary measurement standards for low frequency sound (in both air and water) and vibration. The aim of the task “Development and Evaluation of Primary Calibration Methods in Underwater Acoustics in a Frequency Range from 0.5 Hz to 100 Hz” is to develop and evaluate candidate calibration techniques in underwater acoustics for use as primary standards in frequency range of interest. These methods will be evaluated in terms of their limitations, uncertainty contributions and calibration results. The pressure coupler reciprocity method is based on the hydrophone, a transducer and projector which are calibrated inside a relatively small coupling chamber where the acoustic field is homogenous. Through a series of electrical measurements of voltage and current, the acoustic sensitivity of the three devices may be calculated traceable to electrical primary units.