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We investigate spectro-temporal properties for two black hole X-ray binarysources, MAXI J1535$-$571 and H 1743$-$322, during their hard andhard-intermediate states. For MAXI J1535$-$571, we analyze Swift/XRT, NuSTARand NICER observations, specifically focusing on the occurrence of type-CQuasi-periodic Oscillations (QPOs). Regarding H 1743$-$322, we analyzemulti-epoch observations of NICER and AstroSat, identifying a type-C QPO withcentroid frequency ranging from 0.1--0.6 Hz. In both sources, we fit thespectra with a relativistic truncated disk and a power law component. In MAXIJ1535$-$571, we also observe an additional relativistically smeared iron line.Through temporal and spectral analysis, we estimate the QPO centroid frequencyand spectral parameters, such as the accretion rate and inner disc radii. Wetest the origin of type-C QPOs as relativistic precession frequency and dynamicfrequency (i.e. the inverse of the sound crossing time $\frac{r}{c_s(r)}$). Thedependence of QPO frequency on both the accretion rate and inner disc radiifavours the QPO origin as dynamic frequency. We discuss the implications ofthese results.

Testing the dynamic origin of Quasi-periodic Oscillations in MAXI J1535-571 and H 1743-322