  We demonstrate direct, acoustically mediated spin control of naturally
occurring negatively charged silicon monovacancies (V$_{Si}^-$) in a high
quality factor Lateral Overtone Bulk Acoustic Resonator fabricated out of high
purity semi-insulating 4H-Silicon Carbide. We compare the frequency response of
silicon monovacancies to a radio-frequency magnetic drive via
optically-detected magnetic resonance and the resonator's own radio-frequency
acoustic drive via optically-detected spin acoustic resonance and observe a
narrowing of the spin transition to nearly the linewidth of the driving
acoustic resonance. We show that acoustic driving can be used at room
temperature to induce coherent population oscillations. Spin acoustic resonance
is then leveraged to perform stress metrology of the lateral overtone bulk
acoustic resonator, showing for the first time the stress distribution inside a
bulk acoustic wave resonator. Our work can be applied to the characterization
of high quality-factor micro-electro-mechanical systems and has the potential
to be extended to a mechanically addressable quantum memory.
