A mechanical apparatus of coupled oscillator chains which are levitated on a track by air has been constructed with designing anew nonlinear springs. By use of the apparatus, excitation of mobile type of intrinsic localized modes has been demonstrated with driving sinusoidally at one end of the chains. The apparatus consists of twenty identical oscillators, nonlinear springs, a long and straight air track with a blower at one end and a driver unit for forcing the chains. The oscillators are

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... ected with neighboring ones through the nonlinear springs and levitated above the air track. The relation of restoring force of the spring to deflection is piecewise linear but approximately cubic. In the apparatus with appropriate tensions, the curve of relation is to be symmetrical with respect to the equilibrium position. One end of the chains is fixed and the other is driven sinusoidally in the direction of the chains at a frequency. It has been observed that, driven with a frequency above the cutoff, localized oscillations can be excited intermittently at the driven end and they are propagated along the chains at a constant speed.