Smooth or Stepped? Laboratory Comparison of Enhanced Sonifications for Monitoring Patient Oxygen Saturation

Background: The pulse oximeter (PO) provides anesthesiologists with continuous visual and auditory information about a patient’s oxygen saturation (SpO2). However, anesthesiologists’ attention is often diverted from visual displays, and clinicians may inaccurately judge SpO2 values when relying on conventional PO auditory tones. We tested whether participants could identify SpO2 value (e.g., “97%”) better with acoustic enhancements that identified three discrete clinical ranges by either changing abruptly at two threshold values (stepped-effects) or changing incrementally with each percentage value of SpO2 (smooth-effects). Method: In all, 79 nonclinicians participated in a between-subjects experiment that compared performance of participants using the stepped-effects display with those who used the smooth-effects display. In both conditions, participants heard sequences of 72 tones whose pitch directly correlated to SpO2 value, and whose value could change incrementally. Primary outcome was percentage of responses that correctly identified the absolute SpO2 percentage, ±1, of the last pulse tone in each sequence. Results: Participants using the stepped-effects auditory tones identified absolute SpO2 percentage more accurately ( M = 53.7%) than participants using the smooth-effects tones ( M = 47.9%, p = .038). Identification of range and detection of transitions between ranges showed even stronger advantages for the stepped-effects display ( p < .005). Conclusion: The stepped-effects display has more pronounced auditory cues at SpO2 range transitions, from which participants can better infer absolute SpO2 values. Further development of a smooth-effects display for this purpose is not necessary.

Directional Pulse/Tone Based Channel Reservation with Deafness Avoidance

The use of directional antennas in support of ad hoc networks has been considered a promising alternative to improve spatial division multiple access and throughput. In general, directional Medium Access Control (MAC) protocols are based on IEEE 802.11 standard, which was designed for omnidirectional communication. When applied to di- rectional communication, the standard imposes a number of constraints to the directional MAC protocol. In order to harvest the benefits of directional communications, MAC pro- tocols tailored for directional antennas have to be devised. In particular, MAC protocols that are able to deal with deafness and channel reservation latency are highly desirable. This work proposes a technique that enables channel reservation and mitigates deafness using pulse/tone signals in the context of directional communications. At its heart, the proposed technique incorporates a deafness predictions scheme that helps nodes to over- come its effects. Analytical results show that the proposed technique is able to improve throughput up to 40% when compared to other prominent directional MAC protocols. Simulation results show that the proposed scheme improves fairness and throughput up to 350% and 76%, respectively.

Songbirds use pulse tone register in two voices to generate low-frequency sound

The principal physical mechanism of sound generation is similar in songbirds and humans, despite large differences in their vocal organs. Whereas vocal fold dynamics in the human larynx are well characterized, the vibratory behaviour of the sound-generating labia in the songbird vocal organ, the syrinx, is unknown. We present the first high-speed video records of the intact syrinx during induced phonation. The syrinx of anaesthetized crows shows a vibration pattern of the labia similar to that of the human vocal fry register. Acoustic pulses result from short opening of the labia, and pulse generation alternates between the left and right sound sources. Spontaneously calling crows can also generate similar pulse characteristics with only one sound generator. Airflow recordings in zebra finches and starlings show that pulse tone sounds can be generated unilaterally, synchronously or by alternating between the two sides. Vocal fry-like dynamics therefore represent a common production mechanism for low-frequency sounds in songbirds. These results also illustrate that complex vibration patterns can emerge from the mechanical properties of the coupled sound generators in the syrinx. The use of vocal fry-like dynamics in the songbird syrinx extends the similarity to this unusual vocal register with mammalian sound production mechanisms.