Tire manufactures have dealt with noise problem by varying the pitch of the tread. The various formulas for the variations are generally determined differently, however. Often these variations are based on a combination of trial and error, intuition, and economics. Some manufactures have models and analogs to test tread patterns and their variations. These efforts, however practical, do not determine the best variation beforehand or guarantee the best results. For this reason it was felt that a general mathematical approach for determining the best variation was needed. Moreover, the method should be completely general, easy to use, and sufficiently accurate. This paper discusses a mathematical method called Mechanical Frequency Modulation(MFM) which meets the above requirements. Thus, MFM pertains to computing an irregular time sequence of events so that the resulting excitation spectrum is shaped to a preferred form. The first part of this paper treats the theoretical basis for computing an optimum variation ; the second part discusses experimental results and simulation program which corroborate the theory.

In this paper, we propose a personal-computer-based wireless data access system, which used direct sequence spread spectrum method and the ISM band with 2.44GHz radio frequency. By applying bi-directional transmission between wireless handy terminals and PC or servers, it can be effectively connected with any kinds of database systems such as Oracle, MS-SQL and Access. Therefore it could economically be used as peripheral equipments for ERP or SCM system.