Longitudinal and flexural waves in an infinite plate of an isotropic elastic material can be analytically synthesized from a single dilatational potential function and a single rotational potential function. IfAis the amplitude of the former andBis the amplitude of the latter, it is possible to calculate the ratioA/Bfor a particular mode as a function of frequency once the values of the roots of the appropriate frequency equation are at hand. Calculations of this kind have been carried out for the lowest three longitudinal and lowest three flexural modes and show that, in general, these modes are composite wave motions involving varying combinations of dilatational and rotational components such thatA/Bvaries in amplitude and phase in a given mode as a function of frequency. The primary purpose of this paper is to introduce the “character” of the various modes, defined as [(A/B)(A/B)*], as a concept useful in understanding the selective attenuation of high‐frequency elastic modes in polycrystalline metal strips. In this type of medium, rotational waves are attenuated appreciably more than dilatational waves; hence a given mode might be expected to exist more strongly over the frequency range in which the total wave motion is predominantly dilatational in character. Measurements of the attenuation of elastic pulses having 5 to 35 Mc carrier frequencies and traveling in thin strips of polycrystalline aluminum have been made. In the results, a good correlation is observed between the frequency range over which a given mode is observed and the frequency range over which, theoretically, the character of the mode is large; i.e., [(A/B)(A/B)*]>1.