Reality is everywhere. It is right there in our face when we wake up and it continues to sneak up on us throughout our day, in the car, in our offices, and at the dinner table. In recent years it has even invaded our TVs through eternal news streams and endlessly boring reality TV shows. However, people cannot live by reality alone. In fact, we spend quite a lot off effort on escaping reality. We daydream and immerse ourselves in imaginary worlds and stories. We immerse ourselves in fiction. Inspired by this view, we report on our research into the design and user experience of a new genre of mobile location-based services, which uses peoples' physical surroundings as a backdrop for storytelling as they move around an urban environment. We present a prototype system developed to explore the user experience of location-based interactive stories, and the use of interaction designs aimed at blurring the boundary between reality and fiction. Based on qualitative data from a series of field trials, we discuss potentials and challenges for this class of location-based services.

Active amplifiers within the cochlea generate, as a by-product of their function, distortion-product otoacoustic emissions (DPOAEs) in response to specific two-tone stimuli. Focus has been on invoking emissions in a mid-frequency range from ∼0.5 to 4 kHz. The present study investigates stimulus parameters of the DPOAE at 2f1-f2 frequencies below 0.5 kHz. Eighteen out of 21 young human adults screened had audiometrically normal hearing for inclusion in the experiment. DPOAEs were measured with pure-tone stimuli in four configurations: f2 fixed around 2.13 kHz, f2 fixed around 0.53 kHz, 2f1-f2 fixed at 1.23 kHz and 0.25 kHz. Eight stimulus ratios, f2/f1, and three stimulus sound pressure levels, L1/L2, were measured in each configuration. Trends in ratio-magnitude responses for the mid-frequency DPOAE agree with those reported in previous literature. DPOAEs are not limited to distortion frequencies >0.5 kHz, but the stimulus ratio invoking the largest DPOAE in the mid-frequency range does not do so in the low-frequency range. Guiding the ratio according to the equivalent rectangular bandwidth of auditory filters maintains the DPOAE level.

Swept tones allow the efficient measurement of otoacoustic emissions (OAEs) with fine frequency resolution. Although previous studies have explored the influence of different sweep parameters on the measured OAE, none have directly considered their effects on the measurement noise floor. The present study demonstrates that parameters such as sweep type (e.g., linear or logarithmic), sweep rate, and analysis bandwidth affect the measurement noise and can be manipulated to control the noise floor in individual subjects. Although responses to discrete-tone stimuli can be averaged until the uncertainty of the measurement meets a specified criterion at each frequency, linear or logarithmic sweeps offer no such flexibility. However, measurements of the power spectral density of the ambient noise can be used to construct variable-rate sweeps that yield a prescribed (e.g., constant) noise floor across frequency; in effect, they implement a form of frequency-dependent averaging. The use of noise-compensating frequency sweeps is illustrated by the measurement of distortion-product OAEs at low frequencies, where the ear-canal noise is known to vary significantly.

At constant ratios, the phase of the nonlinear distortion component of the distortion-product otoacoustic emission (DPOAE) has a steep low-frequency segment and a flat high-frequency segment in adults and newborns. In adults, recent work found that a third segment characterizes the phase at even lower frequencies. The present study tests whether the same is true of the newborn DPOAE phase. Newborn and adult phase curves are generally similar. However, as previously reported, phase-gradient delays at mid frequencies (the region of steepest phase slope) are 50% longer in newborns.

The apical and basal regions of the cochlea appear functionally distinct. In humans, compelling evidence for an apical-basal transition derives from the phase of otoacoustic emissions (OAEs), whose frequency dependence differs at low and high frequencies. Although OAEs arising from the two major source mechanisms (distortion and reflection) both support the existence of an apical-basal transition—as identified via a prominent bend (or “break”) in OAE phase slope—the two OAE types disagree about its precise location along the cochlea. Whereas distortion OAEs at frequency 2f1−f2 suggest that the apical-basal transition occurs near the 2.5 kHz place, reflection OAEs locate the transition closer to 1 kHz. To address this discrepancy, distortion and reflection OAEs were measured and analyzed in 20 young human adults from 0.25–8 kHz and at eight primary-frequency ratios f2/f1 in the range 1–1.5. Break frequencies and OAE phase-gradient delays were estimated by fitting segmented linear models to the unwrapped phase. When distortion- and reflection-OAE phase are considered as functions of ln f2—that is, as linear functions of the location of their putative site of generation within the cochlea—the analysis identifies not just two but three main cochlear segments, meeting at transition frequencies of approximately 0.9 and 2.6 kHz, whose locations are largely independent both of primary-frequency ratio and emission type. A simple model incorporating an abrupt transition from wave- to place-fixed behavior near the middle of the cochlea accounts for key features of distortion-OAE phase.