Database for HF Transmitted Speech with Carrier Frequency Difference

<p>This public database is designed for evaluation of carrier frequency difference estimation systems and is published as part of our paper &quot;Open Range Pitch tracking for Carrier Frequency Difference<br> Estimation from HF Transmitted Speech&quot;. It consists of over 23 ours of real transmissions over HF links with a known carrier frequency shift during demodulation.</p> <p>To record the data we have set up a transmission system between our base station in Paderborn and several other distant base stations across Europe (see Fig. 4), transmitting utterances from the LibriSpeech corpus.</p> <p>Kiwi-software defined radio (SDR) devices at distant base stations were utilized to demodulate the received SSB HF signals and send the recorded audio signals back to our servers via a websocket connection. Audio markers had been added to the transmitted signal to allow for an automated time alignment between the transmitted<br> and received signals, easing the annotation and segmentation of the data.<br> For the transmissions a beacon, callsign DB0UPB, was used, which was supervised by a human to avoid interference with other ham radio stations. The HF signals are SSB modulated using the Lower Side Band (LSB) with a bandwidth of 2.7 kHz at carrier frequencies of 7.06 MHz &minus; 7.063 MHz and 3.6 MHz &minus; 3.62 MHz. To simulate a carrier frequency&nbsp; difference the demodulation frequency of the transmitter and the receiver were selected to differ by values from the&nbsp; set [0, 100, 300, 500, 1000]. Although the original speech samples have a sampling rate of 16 kHz, and the&nbsp; Kiwi-SDR samples the data at 12.001 Hz, the finally emitted data is band-limited to 2.7 kHz (International Telecommunication Union (ITU) regulations) which introduces a loss of the upper frequencies in case of LSB<br> transmission depending on the carrier frequency difference. The data set has a total size of 23:31 hours of which 3:28 hours contain speech activity.</p>