Speech scramblers are considered for communication applications where secured speech signal transmissions are important requirement. This paper proposes a frequency voice scrambler with much less residual intelligibility, simulated in Matlab. In this, two techniques, Fast Hartley Transform (FHT) and Orthogonal Frequency Division Multiplexing (OFDM) scrambling key generation scheme are combined together, which can provide scrambled speech by permuting frequency components. Thus the voice cryptographic system is based on an OFDM scrambled discrete Hartley Transform.