Horn - Forward Warning - Electric - Performance, Test, and Application
This document establishes the following criteria for electrically operated forward warning horns on mobile construction machinery: (a) Forward warning horn performance requirements; (b) Measurement technique for horn performance requirements; (c) Laboratory environmental tests; and (d) Horn activation on the vehicle.
Changes to the SAE J1105 document were made to provide tests that are more repeatable and to achieve consistency with other SAE procedures. Revisions have been made to correlate with SAE J994 as much as possible since both backup alarms and horns are utilized on the same work machines. The primary changes and the reasons for them are listed as follows:
a. Broadened the scope of the standard to include nominal system voltages other than 12 and 24 V.
Reason: To establish functional, environmental, and life cycle requirements for horns used in applications with nominal system voltages other than 12 or 24 V, such as battery powered vehicles.
b. Added a maximum horn activation delay of 100 ms. Reason: To insure timely horn activation after power application.
c. Removed sections which gave precautions regarding Multi-Instrument Systems, Calibration, Weather effects and use of windscreens. Reason: Section 5 states a requirement that persons technically trained and experienced in current techniques of sound measurement should select and operate the equipment. Such personnel will be aware of these precautionary measures.
d. Added a definition of "Sample Horn". Reason: To insure that horns tested according to this standard are representative of production.
e. Added requirement that the same sample horn be used for all of the Functional, Environmental, and Life Tests. Reason: To clarify the intent of the standard to eliminate the possibility of a different sample horn being used for each of the test procedures.
f. Revised the predominant sound frequency lower limit requirement from 710 to 250 Hz.
Reason: The majority of vehicle horns are low frequency devices that operate at approximately 350 Hz.
g. Revised the test distance requirement from horn to microphone to reduce the effect of near field measurement errors.