investigation where black boxes were found without debris. >> reporter: indeed, questions about the fleeting signals the chinese picked up remain. for instance, how could a relatively rudimentary detector, this one cost no more than $16,000, designed for use in shallow water pick up pulses potentially miles deep? it's technically possible, but not likely says the pacompany tt makes the detector. >> it would be right at the edge of the detection limit of that system. >> reporter: the signals are the right frequency, but the ocean is noisy. the chinese team wasn't operating in ideal conditions. using earbuds instead of more reliable headsets to listen for the pulses. the team was also traveling with a spare pinger onboard which could have been emitting a signal of its own. and the chinese said they did not have time to record the pulses. making a scientific analysis impossible. one thing is certain, china is eager to show it's working on behalf of the 154 chinese citizens onboard flight 370. >> the chinese government wants