Figure 2. Results shown in Figure 1 compared to results on the same material at 30 Hz collected by Hines, Peters, and Lütjering [31] (TUHH = Technische Universität Hamburg-Harburg), 1500 Hz collected by Davidson [12] (SwRI. = Southwest Research Institute), and 20,000 Hz collected by Mayer and Stanzl-Tschegg [13] (BOKU = Universität für Bodenkultur). While there may be a slight shift in the Paris regime between 1000 Hz and 20,000 Hz, near-threshold behavior appears to be unaffected by frequency.