  Hole spins in semiconductor quantum dots or bound to acceptor impurities show
promise as potential qubits, partly because of their weak and anisotropic
hyperfine couplings to proximal nuclear spins. Since the hyperfine coupling is
weak, it can be difficult to measure. However, an anisotropic hyperfine
coupling can give rise to a substantial spin-echo envelope modulation that can
be Fourier-analyzed to accurately reveal the hyperfine tensor. Here, we give a
general theoretical analysis for hole-spin-echo envelope modulation (HSEEM),
and apply this analysis to the specific case of a boron-acceptor hole spin in
silicon. For boron acceptor spins in unstrained silicon, both the hyperfine and
Zeeman Hamiltonians are approximately isotropic leading to negligible envelope
modulations. In contrast, in strained silicon, where light-hole spin qubits can
be energetically isolated, we find the hyperfine Hamiltonian and $g$-tensor are
sufficiently anisotropic to give spin-echo-envelope modulations. We show that
there is an optimal magnetic-field orientation that maximizes the visibility of
envelope modulations in this case. Based on microscopic estimates of the
hyperfine coupling, we find that the maximum modulation depth can be
substantial, reaching $\sim 10\%$, at a moderate laboratory magnetic field,
$B\lesssim 200\,\mathrm{mT}$.
