Stethoscope A stethoscope was an instrument that amplified sound , allowing the wearer to better hear the sounds emanating from the site on which the bell of the device was placed . Though typically meant for medical practice — as when Harry Sullivan and Martha Jones examined the Doctor ' s heart s ( TV : " Robot " , " Smith and Jones " ) , it could be used in other , non - medical situations . The Doctor , for instance , frequently used it to amplify the sound that mechanical or electronic devices made , ( TV : " Fury from the Deep " , " The Stolen Earth " ) or to eavesdrop on a conversation in an adjacent room . ( AUDIO : " Storm Warning " , TV : " Partners in Crime " ) The Doctor found it such a useful device that many of his incarnations , including Second , Fourth , Eighth , Tenth and Eleventh carried one . Instances of use . By humans . On Earth , most medical students and doctors had stethoscopes , which they used throughout their careers . ( TV : " Spearhead from Space " , " Robot " , " The Hand of Fear " , " The Christmas Invasion " , " Smith and Jones " ) Tina the cleaner ' s lodger was a medical student . Jackie took the lodger ' s stethoscope while she was asleep and Rose then used it to check that both of the newly - regenerated Tenth Doctor ' s heart s were working . When Rose later checked , only one heart was beating . ( TV : " The Christmas Invasion " ) After being checked into the Royal Hope Hospital , the Tenth Doctor was examined by Martha Jones , who used her stethoscope to listen to the Doctor ' s heart . When she did , she found he had two hearts . ( TV : " Smith and Jones " ) By the Doctor . On several occasions , the Doctor used the stethoscope as a non - medical tool . The Second Doctor used a stethoscope to listen to the pipes emanating from the Euro Sea Gas plant . He at first thought he detected a heart beat in the pipes , but dismissed it as the sound of a pump . In fact , he had heard the stirrings of organic life — that of the weed creature . ( TV : " Fury from the Deep " ) The Second Doctor again used a stethoscope to listen for an audio lock in the cell he , Jamie McCrimmon , Zoe Heriot and Lt . Joe Sorba were trapped in . ( TV : " The Space Pirates " ) The Fourth Doctor used a stethoscope to examine Erato ' s spacecraft . He found it the source of a signal he received . ( TV : " The Creature from the Pit " ) The Eighth Doctor carried a stethoscope he had " borrowed " from Arthur Conan Doyle , which he needed to return to Doyle before the writer stopped practising medicine . The Doctor used it to eavesdrop whilst aboard the " R101 " . ( AUDIO : " Storm Warning " ) The Tenth Doctor used a stethoscope to listen at the door to the Thames Flood Barrier . ( TV : " The Runaway Bride " ) The Tenth Doctor used a stethoscope to listen at the window of Adipose Industries . ( TV : " Partners in Crime " ) The Tenth Doctor and Donna Noble used his stethoscope to listen to the two hearts of Jenny whilst imprisoned . ( TV : " The Doctor ' s Daughter " ) The Tenth Doctor also used his stethoscope to listen to the knocking sound on the hull of a shuttle bus during a ride to the Sapphire Waterfall . ( TV : " Midnight " ) When the Earth was taken to the Medusa Cascade , Harriet Jones , Torchwood and Mr Smith all worked together to send a signal to Martha ' s phone . When it rang , the Tenth Doctor answered to find it only to be a signal , which he then followed by using his stethoscope . ( TV : " The Stolen Earth " ) The Eleventh Doctor used his stethoscope to help him fly the TARDIS . ( TV : " The Lodger " ) The Eleventh Doctor put a stethoscope around his neck to prove he was a doctor . ( PROSE : " Shroud of Sorrow " )