We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
Page 3 Assuming for the moment that high fidelity is considered desirable let us consider the question as to whether frequency modulation is the answer to the problem, whether satisfactory results may be obtained by amplitude modulation. A number of studies have been made to determine what the maximum frequency need be for high fidelity transmission. The answer seems to be that very little if any improve¬ ment Is gained by transmitting frequencies above 10,000 cycles* Recent studies with respect to permissible distortion seem to indicate that with wide frequency response the figure must be reduced to two percent. Let us now examine a typical high fidelity system in the light of the above questions. The allowable dynamic range—i.e* volume range between the softest and the loudest passages, is limited on the one hand by the neighbors who will probably object to full volume passages and on the other by the intrinsic noise level of the room. This limits the dynamic range in the listeners room to not more then 60 DB and often as in the case of apartment buildings to a much lower figure. Considerable frequency distortion is introduced by standing waves in the listening room, spatial distribution of the radiated sound, and the variation of aosurption with frequency. Remember, all of these limitations are introduced by environment before the reproducing system is even considered. The next link in the system is the loud speaker. The best speakers at the present time introduce considerable frequency and amplitude distortion. The amplitude distortion is of two types; nonlinear distortion and transient distortion* The second type is most objectionable and contrary to common belief occurs at both low an<I high frequencies. It is a type of distortion which tends to make the high notes sound more piercing than normal. In the audio amplifier of the receiver very little distortion of either type need he introduced. The noise level is up slightly however, knd tends to curtail the dynamio range to a minor degree. All of the distortion considered thus far is oommon to both systems and will not he ohanged. hy the ohange in system of transmission. Taking the next link to he from transmitter input to detector output, it is'agreed that the F. M. system will have a deoided advantage over A.M. with respect to noise level. Therefore the dynamio remge of this section of the transmission system will he wider for F.K. than fox A.M. However the A.M. system oan he made to have a dynamio range of 50 DB. With respect to frequenoy andamplltudedlstortipn the systems oan he made of equal fidelity, although the Bal JaiSZS l Incre ases with an increase of acceptance, band ini the sys . e ^ When we consider the speech inp4t systems which are oommon to both A.M* and F.M. we find that there is a further limitation of the