From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Technical analysis comparing the tonal qualities and harmonics of Klaxon and Bosch car horns.
| Identifier | ExFiles\Box 59\3\ Scan096 | |
| Date | 8th December 1930 | |
| -2- the same time it is somewhat different in quality. The difference in the two-tones of any one horn is brought about merely electrically in such a way that anything (in between) can be made available. If, therefore, "the low tone is too low" this can be raised by altering the quantity of the incorporated inductance or resistance which effects the change. In regard to the high tone, this on the Klaxon is very approximately of the same fundamental frequency as that of the Bosch, and so far as we can see differs mainly in its train of harmonics. In a general way we suppose that the purer fundamental note i.e. greater freedom from harmonics, would be considered more desirable and it is this freedom which Bosch has probably been able to secure -- a freedom depending upon the finer details of material and construction which would not be easily perceived in immitating the Bosch construction. This may be, to some extent, a hypothesis. A suggestion here arises that the relative quality of these tones might be tested by practical harmonic analysis, and it is possible that we may be making a preliminary investigation as to whether anything can be arrived at along these lines. The whole matter is under further investigation. In regard to the adjustment, the effect of this between limits within which the horn will work, is mainly an amplitude or loudness effect and does not materially alter the note or the tone. It may be of interest to remark that Bosch does make a horn of approximately 450 fundamental frequency which is offered for such purposes as fire engines and ambulances. EFC. | ||