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Oslo, Norway – Ultra low power (ULP) wireless specialist Nordic Semiconductor ASA recently announces that a patented medical simulation instrument developed by US firm O'Keefe Electronics employs the Nordic nRF24Z1 2.4GHz RF transceiver to stream wireless audio recordings of human body sounds. The instrument accurately reproduces actual human body sounds to add realism to the training and examined assessment of doctors, nurses and other medical staff.

Lecat's Ventriloscope (www.ventriloscope.com) uses a handheld transmitter and stethoscope-mounted receiver unit to wirelessly transmit authentic heart, lung or bowel sounds selected by a role-playing actor (referred to as a "standardized patient") to a trainee healthcare professional, for diagnosis. (See "About medical simulation" below.) The Ventriloscope can also be used to enhance the realism of sounds on any mannequin used for the same purposes.

In operation, the audio is stored on a Secure Digital (SD) card housed in the transmitter that holds MP3 recordings of sounds taken from real-life patients with the actual disease being simulated. When the trainee healthcare professional places the stethoscope on the relevant part of the actor's body, the transmitter sends the appropriate sound to the earpiece of the stethoscope, accurately mimicking reality.

The transmitter uses a microcontroller to process the MP3 file before it is transmitted by the nRF24Z1 2.4GHz audio streaming transceiver. The receiving unit is equipped with another nRF24Z1 that receives the digitized audio signal, which is passes through a digital-to-analog converter, on to a speaker attached to the stethoscope tube and finally to the trainee healthcare professional's ears. Apart from attachment of the transmission unit, the stethoscope is a standard unit.

Lecat's Ventriloscope reproduces real body sounds with almost complete realism. This is in large part due to the "lossless" audio quality of the nRF24Z1 that uses an impressive 4Mbit/s bandwidth to deliver CD-quality uncompressed wireless audio even if packets have to be resent due to interference. In contrast, competing 2.4GHz wireless audio transceivers have to resort to audio compression techniques to overcome limited bandwidth with a noticeable degradation in sound quality.

The nRF24Z1 also utilizes a proprietary frequency agility protocol to ensure robust wireless streaming even in the presence of other 2.4GHz transmissions sources such as Bluetooth® wireless technology and Wi-Fi® that may be operating in the vicinity. The frequency agility protocol ensures the nRF24Z1 changes to a different communication channel before interference becomes so severe that audio quality is compromised. (See "About the nRF24Z1" below.)

"Realism is vital in health training situations," explains the inventor of Lecat's Ventriloscope, Dr Paul Lecat, MD, FACP, FAAP, who is a board member at Akron General Health Systems and Medical Director of the Wasson Center of Northeastern Ohio Universities Colleges of Medicine and Pharmacy (NEOUCOM). "Yet until now we've had to make do with expensive plastic mannequins using internal speakers that simply did not offer a particularly real or wide ranging training experience due to a limited number of sounds and poor audio quality."

In contrast, Lecat's Ventriloscope is considerably less expensive, yet the quality of the sound experienced by the doctor or nurse is identical to that produced by a real sick patient. The device also enables learning of sounds in the context of a "whole" patient because there is real human interaction. "This is the first time to our knowledge that we have been able to generate ‘sick' sounds from a healthy patient in a realistic way. Integrating the patient's story with the findings on physical examination is a critical skill for all medical personnel and has not been simulated realistically until now," reports Dr Lecat.

"The medical actor can select up to a dozen different sounds per SD card and the stethoscope can be positioned anywhere. And, because we are using digital files, new sounds from actual sick patients can be uploaded to an Internet database for download to the SD card," adds Dr Lecat.

"The nRF24Z1 is the ideal transceiver for this application," says Patrick O'Keefe, Principal of O'Keefe Electronics, the manufacturer of Lecat's Ventriloscope. "The original idea was to use an FM radio, but this would have been too bulky, required an antenna tens of centimeters long and would have been prone to interference. The nRF24Z1 is a compact, inexpensive, leading-edge 2.4GHz transceiver specifically designed for audio streaming that operates with a compact antenna. It offers CD quality wireless audio and is supplied complete with a frequency hopping protocol ensuring high interference immunity.

"A design engineer does not need to be an RF expert to complete a design successfully. With nominal RF experience we completed 90 percent of the design just by using Nordic's two reference designs and evaluation kit, and when we needed technical help, Nordic offered concise advice and checked our overall design. Most importantly, they did several meticulous design reviews of the antenna matching network PCB layout. As a result the design passed its FCC RF compliance test first time. That's something that happens to only 25 percent of RF designs."

"This is an innovative application of our nRF24Z1," says Geir Langeland, Director Sales & Marketing Nordic Semiconductor. "When we designed the nRF24Z1 we didn't anticipate that its sound transmission qualities would see it used in such diverse applications, so to see the transceiver providing the enabling technology for an important medical product is particularly pleasing."

About the nRF24Z1
The nRF24Z1 is a unique single chip solution for wireless streaming of crystal clear CD-quality stereo audio up to16-bit, 48kHz without using compression. The nRF24Z1 also features input support of up to 24-bit, 96kHz.

Operating in the global 2.4GHz band the nRF24Z1 offers unrivalled performance and integration coupled with an ultra-low solution cost. The nRF24Z1 uses Nordic Semiconductor's 4 Mbit/s MegaZtream™ platform embedding a state of the art Quality of Service (QoS) subsystem with an ultra low power robust 4Mbit/s wireless 2.4GHz transceiver and all appropriate digital audio interfaces creating a complete digital wireless audio streamer solution in a 6 by 6mm package. In addition to streaming audio up to 4Mbit/s, the nRF24Z1 also boasts a digital control information channel for transfer of control information such as volume, balance and display details.

Using industry standard I2S and S/PDIF interfaces for audio, the nRF24Z1 can interface without glue logic to virtually any digital audio source, or external industry standard low cost analogue-to-digital and digital-to-analogue converters for analogue audio input and output. Control information uses SPI or 2-wire (I2C compatible).

The nRF24Z1 features a well-balanced design where attention is paid to every detail of the audio interface and the challenging tasks of streaming CD-quality audio with no glitches and degradation in performance in the presence of other 2.4GHz sources such as Bluetooth®. The circuit has embedded voltage regulators, giving maximum noise immunity and operation from a single 2.0 to 3.6V supply.

About medical simulation
Medical simulation with "standardized patients" is an important training technique for healthcare professionals used around the world. The standardized patient is an actor trained to respond to questions and submit to examination so that a student can practice diagnosis of an unknown ailment.

It's important that the simulation is a real as possible so that students learn to deal with the stress of dealing with a sick patient while making an accurate diagnosis.

Unfortunately, the standardized patient technique lacks realism when the student uses a stethoscope to listen to lung, heart and bowel noises, as the standardized patient is not actually ill. An alternative is a medical mannequin equipped with speakers in specific locations reproducing appropriate sounds. This has a number of disadvantages, including forcing the student to move away from the "real" patient, limited numbers of sounds and poor sound quality due to the effect of the mannequin's plastic skin.

In his role as Medical Director of the Wasson Center at NEOUCOM, Dr Paul Lecat became concerned that simulations using plastic mannequins were not providing enough realism.

"As Medical Director of a major simulation centre with a nationally recognized standardized patient program, I was frustrated by excellent case portrayals being suddenly ruined by the lack of credible physical exam findings," explains Dr Lecat. "Physical exam itself lost credibility as it was relegated to what was reported on paper, not what was actually discovered by the student. There was little or no incentive to really do a good physical exam and many students were simply going through the motions."

To dramatically improve realism, Dr Lecat developed Lecat's Ventriloscope, a stethoscope that reproduces CD quality recordings of real sounds from sick patients. The recordings are stored on an SD Card plugged into a handheld transmitter and replayed by the standardized patient when a stethoscope is placed on the patient's body. The Ventriloscope uses RF wireless connectivity to send the audio file from the transmitter to the receiver attached to the stethoscope.

SOURCE: Nordic Semiconductor ASA