A circular flow tank facility has been developed which features extremely low acoustic and vibration ambient conditions. This facility is described, operating procedures associated with its use are presented, and limitations in the measurement procedures are mentioned. The flow facility has been used to measure the noise output of pressure and pressure gradient hydrophones during actual flow conditions and results of these tests are presented and discussed. [This work was sponsored in part by the Naval Air Development Center.]

An artificial ear was designed to simulate the mechanical and acoustical properties of the external ear, up to and including the impedance of the eardrum. The sensing element is a B & K 4132 electrostatic microphone terminating a simulated earcanal with an acoustical impedance-matching network that, combined with the microphone, furnishes the eardrum impedance. The canal proper has dimensions approximating those of the real ear and is surrounded by a plastisol pinna of realistic dimensions and texture. The new artificial ear is suitable for testing all types of receivers and ear enclosures under realistic conditions. The inner portion of the artificial ear is made of reproducible metallic components, making it suitable for consideration as an artificial-ear standard. [Work supported by NASA-Manned Spacecraft Center, Houston, Texas.]

The BASE collaboration at the antiproton decelerator/ELENA facility of CERN compares the fundamental properties of protons and antiprotons with ultra-high precision. Using advanced Penning trap systems, we have measured the proton and antiproton magnetic moments with fractional uncertainties of 300 parts in a trillion (p.p.t.) and 1.5 parts in a billion (p.p.b.), respectively. The combined measurements improve the resolution of the previous best test in that sector by more than a factor of 3000. Very recently, we have compared the antiproton/proton charge-to-mass ratios with a fractional precision of 16 p.p.t., which improved the previous best measurement by a factor of 4.3. These results allowed us also to perform a differential matter/antimatter clock comparison test to limits better than $$3\,$$ 3 %. Our measurements enable us to set limits on 22 coefficients of CPT- and Lorentz-violating standard model extensions (SME) and to search for potentially asymmetric interactions between antimatter and dark matter. In this article, we review some of the recent achievements and outline recent progress towards a planned improved measurement of the antiproton magnetic moment with an at least tenfold improved fractional accuracy. Graphic Abstract

A decade ago, two of the authors presented a paper reporting on diffraction and interaural delay of a progressive wave caused by the human head [J. Acoust. Soc. Am. 36, 1993(A) (1964)]. Six live subjects were used in those experiments. The publication was delayed pending measurements on artificial heads then being planned. In this paper, two series of data obtained with the aid of the Acoustical Manikin [J. Acoust. Soc. Am. 42, 204–207 (1967)] are compared with the earlier experiments: (a) Data based on phase measurements; (b) Data obtained using a bandwidth-limited delta pulse. All three methods provide useful information about interaural diffraction and delay, albeit the third method appears to be the most reliable.