periods against the orbital ones, where the periods are in days. Even with a small sample, 11 systems at present, we claimed sufficient evidence of a correlation. One possible explanation would be that according to this empirical correlation, the longer the orbital period of a binary, the longer the pulsation period of its pulsating primary. The $P_{puls}-P_{orb}$ relation appears to be a simple linear form, the following numerical relation was obtained by linear least squares method,

$$log P_{puls} = 0.425(\pm 0.016) \times \log P_{orb} - 0.355(\pm 0.087).$$

The correlation coefficient for this relationship is about 0.79, indicating its significance. The scatter appears to increase towards the shorter orbital periods.

Although the sample contains eleven pulsating primary stars and existence of a considerable scatter in the observed pulsation frequencies a connection between pulsation and orbital periods seems to exist in the $\gamma$-Dor type stars as pointed out by [@soy] for the $\delta$-Sct stars. The pulsation periods are proportional to the orbital periods as $P^{0.43}$. This relation indicates that the shorter orbital period the smaller pulsation period. For the $\delta$-Sct stars in close binaries [@lia] find a relationship as $P_{puls}$ proportional to $P_{orb}^{0.58}$.

Recently [@zhang] indicated that the upper limit of $P_{puls}/P_{orb}$ 