Uni-cone to Stethoscope, The Bodies Auscultation

A Stethoscope, along with a white lab coat, used to be the tools we most associated with doctors and consultants.
Using a stethoscope meant your doc knew about sound, your doctor would need a good ear. This extremely useful tool has been around, in one form or another, for hundreds of years – by listening to the inner audio of the human body you can hear the rhythm of life, even a newborn heartbeat.
It’s uses, in medical and midwifery has been well documented over the centuries but I’m going to cover the last two centuries and what we can tell is going on inside the body by listening using this valuable instrument.
The Stethoscope as we know it today is attributed to R T H Laennec. I have to say it is rather difficult to believe as I understand wooden and ceramic cones were used in midwifery. It ought to be noted that Sumerian cones are dated to around 5000 years ago.
For our purposes, it appears that in 1816 Laennec used a wooden cylinder (or a paper cone) to transmit heart sounds to the ear and documented it. Some years later in 1828 someone called Poirry modified it by adding an earpiece and a trumpet shaped chest piece. Although Poirry stethoscopes are still available and in use today, Auscultation objects, are likened to antique curiosities.
However, it was not until 1850 that the binaural stethoscope that docs really started to investigate those conditions of the respiratory, circulatory, and digestive systems through their auditory channels.
Sounds of your inner body workings, your organs, vascular system, digestive system and most importantly, mitral diastolic murmurs of the heart can all be heard via a stethoscope. These sounds can tell a physician whether the heart and lungs are healthy. Doctors can diagnose a heart murmur by using their stethoscope, lung diseases can be detected in this manner – saving costly scans and all before the electronic equipment can be plugged in.
Most sounds of interest to a doctor especially heart sounds have frequencies in the range 60 to 600 Hz, but some mitral diastolic murmurs (irregular sounds heard over the heart during expansion of the heart and indicating an abnormality in the mitral valve) have frequencies below 60 Hz, and a few sounds , such as crepitations (crackling sounds heard over the chest in some disease of the lungs), have frequencies of up to 1400 Hz. Acoustic stethoscopes do not amplify sound they commute it to the ear as efficiently as possible.
In 1977 stethoscopes started looking more the part. They usually had a combined bell and diaphragm chest piece made of stainless steel. The bell section of the chest piece remains open and has a diameter of 2.87 cm and is 0.64 cm deep.
When this side of the stethoscope is in use, the patients skin acts as flexible diaphragm across the mouth of the bell to transmit the sound. The diaphragm section has s diameter of 4.37 cm but is only 0.33 cm deep. It is covered by a rigid linen Bakelite diaphragm. The larger surface area enabling sound to be picked up.
The doctor can select either side of the chest piece by rotation it relative to the sound collecting tube connecting it to the earpiece tubing. The bell side of the instrument would be used by the doctor to listen to relatively low pitched sounds in the range of about 30 -500 Hz, whereas the diaphragm side of the chest piece is designed to filter out the lowest sounds but pass the highest frequencies in the range 200 to 1400 Hz.
The stethoscope tubing is made of flexible plastic material with a very smooth interior surface and the earpiece tubes were generally made of stainless steel. The design of the plastic tips for the earpieces is surprising important. They must as large as possible usually with a diameter of from 1.27 cm -1.60 cm so that external sounds are blocked from the ears.
A leak of five times the diameter of a human hair has a marked effect on the performance of the stethoscope, particularly at low frequencies. Thankfully stethoscopes have continued to move with the times and got smaller and more efficient at filtering out external sounds. There are a wide range of stethoscopes available today in 2019.
Stethoscopes have come into the digital age. One of the most impressive on the market is the latest offering from Thinklabs One. The device itself fits entirely into the single chest piece and works with any headphones of your choice. It can amplify sounds by more than 100 x.
The device can connect to tablets and smartphones to visually display the waveform of the audio using a matching app, which can also record and let doctor zoom in on specific spots in the recordings. The software provides a variety of audio filtering options to better hear heart murmurs, diastolic rumbles and lungs sounds.
Additionally, the iMurmur app from Thinklabs provides a library of pre-recorded heart sounds that can be used to learn and maybe even compare against one’s own patients. The standard package comes with a set of in-ear headphones, and for the modern physician there’s also the Beats Package that comes with Dr. Dre’s Executive headphones that feature noise cancelling technology.
Looking to the future it is already looking bright for this old medical wonder of technology, the cone developed into the stethoscope and is still has use in midwifery today. The humble cone can still pick up the heartbeat more reliably than the electronic version in pregnancy.
A stethoscope used properly can diagnose major illnesses saving time and discomfort for the patient. Now that it is digital the doctor doesn’t have to remember the sounds or even have a good ear – they just need to know what they are looking for.