Seismic signals can be extracted from ambient noise wavefields by the correlation technique. Recently, a prominent P‐type phase was observed from teleseismic noise correlations in the secondary microseism period band. The phase is named Pdmc in this paper, corresponding to its origin from the interference between the direct P waves transmitting through the deep mantle and the core (P and PKPab waves). We extract the phase by correlating noise records from two seismic networks in the Northern Hemisphere and locate the microseism sources that are efficient for the Pdmc construction in the South Pacific. We investigate the spatiotemporal links of the Pdmc signal with global oceanic waves and microseism sources. Interestingly, the correlation with wave height is higher in several regions surrounding the effective source region, rather than in the effective source region. The Pdmc amplitude is highly correlated with the power of the effective microseism sources. Also, it is apparently correlated with ineffective sources in the Southern Hemisphere and anticorrelated with sources in the Northern Hemisphere. We ascribe the correlation with the ineffective southern sources to the spatiotemporal interconnections of the southern sources. The anticorrelation with northern sources can be explained by the reverse seasonal patterns between the southern and northern sources and by that the northern sources impede the signal construction. The signal construction from noise correlations relies on the competition between the effective and ineffective sources, not just on the power of the effective sources. This principle should be valid in a general sense for noise‐derived signals.