freq = erbtofreq(erb);
This is a wrapper around audtofreq that selects the erb-scale. Please see the help on audtofreq for more information.
The following figure shows the corresponding frequencies for erb values up to 31:
erbs=0:31;
freqs=erbtofreq(erbs);
plot(erbs,freqs);
xlabel('Frequency / erb');
ylabel('Frequency / Hz');