摘要:

The first experiments in stereophony took place at the end of last century, but no serious developments occurred until the advent of the ‘talkies’ about 30 years ago when the cinema industry began actively to investigate the problem. About that time, when developments of cinema stereophony were in progress, Blumlein investigated the position very fully and patented microphone and loudspeaker systems for stereophony, together with methods of recording the information in a single groove on a gramophone record. He also considered domestic stereophony. Lack of satisfactory commercial methods of recording and reproduction, however, prevented developments in the domestic field.The present great interest in stereophony is entirely due to the fact that, by the improvement of recording techniques, it is now possible to make gramophone records with the stereophonic information on the opposite sides of the same groove. The standards have been chosen so that a monophonic pick-up will add the left- and right-hand information to produce a result which is asserted to be ‘compatible’ for monophonic purposes. The implications behind the assumption that the addition of left- and right-hand signals gives ‘compatibility’ are not well appreciated. Monophonic microphone techniques are therefore discussed, followed by the corresponding techniques for stereophony, so that comparisons can be made. It is then revealed that the best microphone positions for monophony and stereophony frequently differ considerably and are often quite incompatible. This poses problems for recording companies and broadcasting organizations for which there may be no easy solution, although undoubtedly some compromise may be found which will be acceptable to both monophonic and stereophonic listeners. There will, however, remain certain types of programme material, especially in broadcasting, in which such compromises may be impossible.Various workers have investigated the requirements for stereophonic transmission, and most of them appear to be in favour of coincident microphones on the ground that the images produced are sharper than with spaced microphones. However, some organizations use spaced microphones, and, in these circumstances, it is claimed that, although the images may not be so sharp as those given by coincident microphones, the position of the listener with respect to the loudspeakers is less critical.In view of the obvious need to monitor the programme material at source, consideration is given to the listening conditions, and some related work in connection with monophonic listening rooms is described.With regard to loudspeakers, various investigators have claimed that it is possible to devise loudspeaker polar characteristics which will keep unchanged the ratio of sound level from both loudspeakers irrespective of the position of the observer in the listening room.

DOI:10.1049/pi-b-2.1959.0043

出版商:IEE    

年代:1959

数据来源: IET

DOI:10.1049/pi-b-2.1959.0044

出版商:IEE    

年代:1959

数据来源: IET

DOI:10.1049/pi-b-2.1959.0045

出版商:IEE    

年代:1959

数据来源: IET

DOI:10.1049/pi-b-2.1959.0048

出版商:IEE    

年代:1959

数据来源: IET

DOI:10.1049/pi-b-2.1959.0049

出版商:IEE    

年代:1959

数据来源: IET

DOI:10.1049/pi-b-2.1959.0050

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Broadcasting, as a medium for the dissemination of stereophonic programmes, presents a number of technical and economic problems over and above those encountered in the production of commercial recordings. Although much of the programme material at present broadcast could, as far as technical quality is concerned, be equally well, or in some cases better, produced by prerecording, certain types of item still require to be transmitted ‘live’. In stereophonic transmissions, various problems associated with the disposition and movement of artists in the studio are then aggravated, while difficulties are encountered in the distribution of the programme over long trunk routes because of fortuitous differences in time delay between the left- and right-hand channels.Various methods have been proposed for broadcasting simultaneous monophonic and stereophonic versions of the same programme without an increase in the number of transmitters. To this end, the monophonic and stereophonic signals are derived from the same set of microphones, a compromise which in some cases makes it difficult to achieve complete compatibility, i.e. optimum performance in both systems simultaneously. Possible methods for achieving compatible monophonic and stereophonic transmissions on a single channel include frequency- or time-division multiplex, involving in some cases a combination of phase- and amplitude-modulation. Most of these systems require some increase in radiated power for a given service area, but others, still under development, aim at overcoming this difficulty by confining the directional information transmitted to one or more narrow-band ‘steering’ signals.In television transmission the judicious use of stereophony could enhance the realism of the picture, but in all but the simplest cases, the microphone technique necessary to avoid incongruity between vision and sound would probably make the latter unsuitable for monophonic reception in the sound service.The engineering effort required to provide nation-wide stereophonic broadcasting without detriment to existing services could be justified only by a sufficient public demand; this last factor depends in turn on the potentialities of stereophony when applied to a wide variety of programmes, a subject which has yet to be fully explored.

DOI:10.1049/pi-b-2.1959.0053

出版商:IEE    

年代:1959

数据来源: IET

摘要:

The purpose of the system is to provide a stereophonic signal for radio transmission within a bandwidth only slightly greater than that required for ordinary monophonic transmission. The left and right microphone signals are combined to form a single a.f. signal which is available for ordinary monophonic reception. They are also processed in such a way as to emphasize the beginnings of sounds and then utilized to form a signal, with a bandwidth of 100 c/s, carrying the directional information only. This directional signal is caused to modulate a sub-carrier at a power level much lower than that of the a.f. signal. In the receiver the a.f. signal and the directional signal are applied to a Hall multiplier unit giving the required left-loudspeaker signal as one output and the right-loudspeaker signal as the other.

DOI:10.1049/pi-b-2.1959.0054

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Consideration is given to the v.h.f. transmission of stereophonic programmes, restricted to f.m. transmitters with a sub-carrier system. Criteria are given, indicating the superiority of the so-called double f.m. system, which has a much smaller deviation than usual of the main carrier due to the sub-carrier, the deviation of which is reduced to only 15 kc/s. A circuit description is given of both the transmitter duplexer and the adaptor necessary for ordinary f.m. receivers. Special attention has been paid to applications of sub-carrier systems other than for stereophony. These lead to more stringent requirements for the crosstalk attenuation.

DOI:10.1049/pi-b-2.1959.0055

出版商:IEE    

年代:1959

数据来源: IET

DOI:10.1049/pi-b-2.1959.0058

出版商:IEE    

年代:1959

数据来源: IET