We report on the development of a compact commercial instrument for measuring carotenoids in skin tissue. The instrument uses two light-emitting diodes (LEDs) for dual-wavelength excitation and four photomultiplier tubes for multichannel detection. Bandpass filters are used to select the excitation detection wavelengths. The f1.3 optical system has high optical throughput and single photon sensitivity, both of which are crucial in LED-based Raman measurements. We employ a signal processing technique that compensates for detector drift and error. The sensitivity and reproducibility of the LED Raman instrument compares favorably to laser-based Raman spectrometers. This compact, portable instrument is used for noninvasive measurement of carotenoid molecules in human skin with a repeatability better than 10%.

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As part of a sound system evaluation at Brigham Young University's football stadium, measurements were made before and during games by an upper-level undergraduate acoustics class. The measurement experience provided significant training opportunities for the students. Teams of students used sound level meters to make recordings at numerous locations both inside and outside the stadium. These measurements were then correlated with data from stationary microphones placed near the field. From the data, the predicted slow, A-weighted equivalent levels in and around the stadium were calculated relative to a sideline location. Straightforward outdoor sound propagation prediction methods involving geometric spreading, atmospheric absorption, barriers, etc. were successfully used to validate the measured data within 1-2 dB at many locations, including one in the foothills to the southeast of the stadium at a distance of approximately 2.7 km. The students appreciated the hands-on experiences gained by participation in the measurements and analysis.

We have developed a compact portable instrument for resonance Raman spectroscopy of carotenoid molecules in skin tissue. Our application focuses on the 1525 cm −1 Raman line common to all carotenoids. We use a divided shifted Raman spectroscopy (DSRS) technique that reduces sensitivity to detector drift and error. Two wavelength-narrowed LEDs illuminate the sample, and scattered light in four different wavelength channels is measured. This multi-spectral approach has single-photon sensitivity and compares favorably with laser-based Raman measurements in terms of accuracy, repeatability, and measurement time.

Directivity measurements for live performance of musical instruments present several experimental challenges, including the need for musicians to play consistently and reproducibly. Some researchers have chosen to implement fixed, limited-element microphone arrays surrounding instruments for rough directivity assessments. Unfortunately, with practical numbers of microphones and data acquisition channels, this approach limits spatial resolution and field decomposition bandwidth. Higher-resolution data may be obtained with a given microphone and channel count by rotating a musician in sequential azimuthal angle increments under a fixed semicircular microphone array. The musician plays a selected note sequence with each increment, but corrections must be made for playing variability. This paper explores the development of this method, which also uses rotating reference frame microphones and frequency response function measurements. The initial developments involve a loudspeaker, with known directivity, to simulate a live musician. It radiates both idealized signals and anechoic recordings of musical instruments with random variations in amplitude. The presentation will discuss how one can reconstruct correct source directivities from such signals and the importance of reference microphone placement when using frequency response functions. It will also introduce the concept of coherence maps as tools to establish directivity confidence.