Research is carried out in the field of applied and physical acoustics. Measurement services to users include calibration of transducers and instruments, such as microphones, sound level meters, acoustic calibrators and sound sources. Certification activity concerns the measurement of the acoustic properties of materials.

Draft B for EUROMET.A-K3 key comparison was completed and approved in the CCAUV meeting. Pattern evaluation of sound level meters was carried out; a considerable amount of data useful for the evaluation of uncertainty of free field comparisons of microphones and instrumentation for measurement of noise was collected during the measurements.

The EUROMET project 879 "Bilateral comparison of ultrasonic power (10 mW to 15 W) in the frequency range from 1.8 MHz to 11 MHz" has been successfully completed, a new CMC on ultrasonic power has been submitted and is now under regional (EUROMET) evaluation.
An apparatus for the measurement of the physical properties of gels used in ultrasound medical applications has been built and tested. Pulse echo techniques are used for comparing the properties of the gel under test with those of ultra pure water, that are well known. The aim is to be able to characterise the ability of the materials to improve ultrasound diagnostic image contrast.
The scanning tank measurement system has been improved both in the transducer positioning mechanism and in signal acquisition, based on a high speed A/D PC card. The ultrasound field of transducers and all the parameters (thermal, mechanical) related to safety of ultrasound medical equipment can be measured.

The knowledge of the physical properties of sound absorbing materials enables the use of mathematical models of enclosures (like theatres, car cabins) for the prediction of acoustical performances.
An accurate measurement of flow resistance is necessary for the calculation of the absorption coefficient of many kinds of materials. An apparatus for the measurement of the flow resistance of materials at very low frequencies (2 Hz) has been built. The method based on a low frequency alternating flow is capable of better uncertainties than the direct flow method.
The apparatus developed at INRIM has the capability of loading the material under test with predetermined pressures, in order to be able to measure the flow resistance in conditions comparable to the actual working conditions.

INRIM participates in the international research effort for the determination of the molar gas constant R and the Boltzmann constant k with 1 ppm uncertainty, by developing an experiment which makes use of a primary acoustic thermometer and involves contemporary measurements of the acoustic and microwave resonant frequencies in a stainless steel spherical resonator. For the purpose of reducing the uncertainty associated with the absolute determination of the volume of the cavity, in 2006 measurements were performed, in argon and helium, when the two hemispheres comprising the resonator were misaligned. The most important result was the determination of the radius of the resonator as a function of pressure with an estimated uncertainty of 2.5 ppm. This work is carried on in cooperation with the Thermal Metrology Section.

As part of an ongoing research program to measure the thermodynamic properties of liquids, accurate measurements of speed of sound in pure acetone have been performed, in pressure and temperature ranges in which new experimental data are needed. Measurements were performed along eleven isotherms for temperatures between 248.15 K and 298.15 K and at pressures from 0.1 MPa up to 100 MPa. The overall estimated uncertainty is in the order of 0.1%. The results agree within the respective uncertainties with the prediction of the NIST Standard Reference Database and with other data available in the literature. The results have been useful in the updating of a new global equation of state and in the calculation of density and constant pressure heat capacity of acetone.

The chemical effects of ultrasounds arise from acoustic cavitation, that is the formation, growth and implosive collapse of bubbles in the liquid, which generates transient temperatures of about 7000 K, pressures of 2000 atm and a cooling rate of 10⁹ K/s. These extreme conditions can drive chemical reactions such as oxidation or reduction and can be used for reducing particle size. Recently smaller size particles were obtained from sonication of silicon Q-dots. The very high temperature reached by the gas phase during single bubble transient cavitation boosted the research into the feasibility of cavitation-induced nuclear fusion reactions. Our laboratory participates in the INFN (Istituto Nazionale di Fisica Nucleare) project SAFE, (Search for Acoustically-induced nuclear Fusion on Earth) aimed at verifying recent claims about neutron production by deuterated organic solvents.