Linear Electron Accelerators for Deep X-ray Therapy

S OF RECENT SCIENTIFIC PUBLICATIONS OF N.V. PHILIPS' GLOEILAMPENFABRIEKEN Reprints of these papers not marked with an asterisk • can be obtained free of charge upon application to Philips Electrical Ltd., Century House, Shaftesbury Avenue, London W.C.2. 2161: R. Vermeulen: Sound recording. General review, presented at the first I.C:A. Congress on Electro-accoustics, Delft, 1953 (Acustica 4, 17-21, 1954.) General considerations on sound recording. The following topics are dealt with; improvements in gramophone records, gramophone recording and reproduction, tape recorders; information, theory in relation to reproduetion of music, fidelity of the reproduction, stereophony, artificial reverberation. 2162: J. Rodrigues de Miranda: The radio set as an instrument for the reproduetion of music (Acustica 4,38-41, }954). In connection with the reproduetion of music by radio the following desiderata are put forward: 1. Distortion should be decreased. as the high frequency range increases. 2. Means are desirahle for adjusting bass response, for cutting óff and for gradual attenuation of treble, 3. The electro-acoustical engineer and the architect should cooperate closely. The cabinet must he rigid, the loudspeaker placed forward; its cloth chosen carefully. 4. The speaker should be chosen in accordance with the acoustical properties of the .cabinet, The audio-frequency characteristic of the set should' he carefully determined. 2163: W. K. Westmijze: Application of the reciprocity theorem to magnetic reproducing heads (Acustica 4,50-52, 1954). 'ill!) , It is shown that the output of a magnetic reproducing head can be calculated if the field distribution in front of the head is known for the case when the latter 'is energised, Application of this method' enables us to predict the response curve of a wideg'ap head and to explain the existing difference between wide-gap and narrow-gap measurements. 2164: A. G. Th. Becking and A. Rademakers. Noise in condenser microphones (Acustica' 4,96-98, 1954). It is pointed out that the mecha'nical resistance, used for damping a simple mechanical oscillator, acts as the source of á fluctuating force with spectral intensity 4RkT. In the case of a eondenser microphone this results in a noise pressure on the diaphragm, which lies in the region of audible sound pressures. Experimental -results, obta~ed with two microphones, agree well with th~ theory. . ' ., 2165: A. G. Th. Beckint Methods of measurement for hearing aids (Acustica 4, ~43-145, 19~4). The different ways of defining the input soillid pressure on a hearing aid are discussed. In addition, a comparison is given of thespecifications for 'acceptable hearing ai~s in s?me Europeancountries. 2166: J. Volger, J. M. Stevels and C. van Amerongen: The dielectri~ l'elaxati0!1 of glass and the pseudo-capacity of metal-to-glass interfaces, measured at extremely low frequen~ cies. (Philips Res. Rep. 8, 452-470, 1953, No.6).