A medical system, comprising: a first sensing electrode (30, 49) configured to contact tissue of a first living subject; a second sensing electrode (30, 49) configured to contact tissue of a second living subject; a recording apparatus; processing circuitry; and a recording apparatus cable extending between the recording apparatus and the processing circuitry; wherein the processing circuitry is configured to: receive first cardiac signal segments responsively to electrical activity sensed by the first sensing electrode in contact with the tissue; inject the received first cardiac signal segments into the recording apparatus cable, the cable being configured to output corresponding noise-added cardiac signal segments responsively to electrical noise acquired in the cable; receive the noise-added cardiac signal segments; train an artificial neural network to at least partially compensate for electrical noise that will be added to cardiac signals in the cable responsively to the received first cardiac signal segments and the corresponding noise-added cardiac signal segments; receive a second cardiac signal responsively to electrical activity sensed by the second sensing electrode in contact with the tissue of the second living subject; apply the trained artificial neural network to the second cardiac signal yielding the second cardiac signal with noise-compensation, which at least partially compensates for the electrical noise, which is not yet in the second cardiac signal but will be added to the second cardiac signal in the cable; and output the second cardiac signal with the noise-compensation to the recording apparatus via the cable. a first sensing electrode (30, 49) configured to contact tissue of a first living subject; a second sensing electrode (30, 49) configured to contact tissue of a second living subject; a recording apparatus; processing circuitry; and a recording apparatus cable extending between the recording apparatus and the processing circuitry; wherein the processing circuitry is configured to: receive first cardiac signal segments responsively to electrical activity sensed by the first sensing electrode in contact with the tissue; inject the received first cardiac signal segments into the recording apparatus cable, the cable being configured to output corresponding noise-added cardiac signal segments responsively to electrical noise acquired in the cable; receive the noise-added cardiac signal segments; train an artificial neural network to at least partially compensate for electrical noise that will be added to cardiac signals in the cable responsively to the received first cardiac signal segments and the corresponding noise-added cardiac signal segments; receive a second cardiac signal responsively to electrical activity sensed by the second sensing electrode in contact with the tissue of the second living subject; apply the trained artificial neural network to the second cardiac signal yielding the second cardiac signal with noise-compensation, which at least partially compensates for the electrical noise, which is not yet in the second cardiac signal but will be added to the second cardiac signal in the cable; and output the second cardiac signal with the noise-compensation to the recording apparatus via the cable. receive first cardiac signal segments responsively to electrical activity sensed by the first sensing electrode in contact with the tissue; inject the received first cardiac signal segments into the recording apparatus cable, the cable being configured to output corresponding noise-added cardiac signal segments responsively to electrical noise acquired in the cable; receive the noise-added cardiac signal segments; train an artificial neural network to at least partially compensate for electrical noise that will be added to cardiac signals in the cable responsively to the received first cardiac signal segments and the corresponding noise-added cardiac signal segments; receive a second cardiac signal responsively to electrical activity sensed by the second sensing electrode in contact with the tissue of the second living subject; apply the trained artificial neural network to the second cardiac signal yielding the second cardiac signal with noise-compensation, which at least partially compensates for the electrical noise, which is not yet in the second cardiac signal but will be added to the second cardiac signal in the cable; and output the second cardiac signal with the noise-compensation to the recording apparatus via the cable.