We present a power spectrum analysis of the long ASCA observation of Ark 564 in June/July 2001 .
The observed power spectrum covers a frequency range of \sim 3.5 decades .
We detect a high frequency break at \sim 2 \times 10 ^ { -3 } Hz .
The power spectrum has an rms of \sim 30 \% and a slope of \sim - 1 and \sim - 2 below and above the break frequency .
When combined with the results from a long RXTE observation ( Pounds et al .
2001 ) , the observed power spectra of Ark 564 and Cyg X-1 ( in the low/hard state ) are almost identical , showing a similar shape and rms amplitude .
However , the ratio of the high frequency breaks is very small ( \sim 10 ^ { 3 - 4 } ) , implying that these characteristic frequencies are not indicative of the black hole mass .
This result supports the idea of a small black hole mass/high accretion rate in Ark 564 .