| 摘要 |
A rigid, earth-contacting target for use with an acoustic signal generator is designed to be impacted by a mass propelled downwardly by compressed air or other energy source. The target includes an upper impact-receiving member slidably interfitted with a lower ground-contacting member. An elastomeric disc is confined between the upper and lower members so as to experience three-dimensional compression in response to such impact. The bulk modulus of the elastomer determines the degree to which the rate of acceleration of the lower member is reduced as compared to that of the upper member, and thus in turn, controls the frequency content of the resultant acoustic pulse.
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