A new method to explore the spectral impact of the piriform fossae on the singing voice : Benchmarking using MRI-based 3D-printed vocal tracts

The piriform fossae are the 2 pear-shaped cavities lateral to the laryngeal vestibule at the lower end of the vocal tract. They act acoustically as side-branches to the main tract, resulting in a spectral zero in the output of the human voice. This study investigates their spectral role by comparing numerical and experimental results of MRI-based 3D printed Vocal Tracts, for which a new experimental method (based on room acoustics) is introduced. The findings support results in the literature: the piriform fossae create a spectral trough in the region 4–5 kHz and act as formants repellents. Moreover, this study extends those results by demonstrating numerically and perceptually the impact of having large piriform fossae on the sung output

The FORBIO Climate data set for climate analyses

Abstract. In the framework of the interdisciplinary FORBIO Climate research project, the Royal Meteorological Institute of Belgium is in charge of providing high resolution gridded past climate data (i.e. temperature and precipitation). This climate data set will be linked to the measurements on seedlings, saplings and mature trees to assess the effects of climate variation on tree performance. This paper explains how the gridded daily temperature (minimum and maximum) data set was generated from a consistent station network between 1980 and 2013. After station selection, data quality control procedures were developed and applied to the station records to ensure that only valid measurements will be involved in the gridding process. Thereafter, the set of unevenly distributed validated temperature data was interpolated on a 4 km × 4 km regular grid over Belgium. The performance of different interpolation methods has been assessed. The method of kriging with external drift using correlation between temperature and altitude gave the most relevant results

Precipitation climate maps of Belgium

Investigations are conducted to best estimate precipitation climate maps over Belgium from daily observations available for the period 1981–2010. Several mapping approaches are compared in a cross-validation exercise. These approaches differ by several aspects and in particular by the order in which the temporal aggregation (i.e. computation of climate mean values from daily data) and spatial interpolation steps are performed, and by the integration of ancillary information in the spatial interpolation method. The selected approach is used to derive a large panel of climate maps. In particular, the main spatio-temporal features of the annual cycle of rainfall in Belgium are extracted by principal component analysis (PCA)

The hypopharynx cavities in the Vocal Tract.

<p>Vocal Tract profile superimposed on an MRI midsagittal slice of a singer while phonating on the vowel as in the word /stːn/ and on a 3/4, details of the hypopharynx cavities which consist of the laryngeal vestibule, the laryngeal ventricles and the two piriform fossae, located posteriorly at the bottom of the pharynx.</p

Singers' data.

<p>Age, classification according to the Bunch and Chapman criteria <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0102680#pone.0102680-Bunch1" target="_blank">[30]</a>, Fach, range, sung pitch (between brackets for falsetto), token(s) sung for the 3 professional singers.</p

Overview of the experimental method.

<p>An Exponential Sine Sweep () is given as an input signal to the driver (1). The output recorded via a probe microphone is convolved with the inverse filter () (2). It results in a temporal separation of the Linear Impulse Response (LIR) and the harmonic distortions (3). An FFT is performed on the LIR to give the linear transfer function of the system (4). Processes 1 to 4 are repeated twice: once with the Vocal Tract, and once without. Both spectra are then subtracted (logarithmic vertical scale) to give the transfer function of the standalone Vocal Tract.</p

Pre- and post-envelope applied to the Exponential Sine Sweep ().

<p>An Exponential Sine Sweep () of the form (1) has a burst of energy across the whole spectrum both at its start and at its end (A1). Once convolved with its inverse filter (A2), it leads to an impulse response and its echoes in the frequency-time space (A3). Providing a smooth start to the () (B1), and convolving it with its inverse filter (B2) removes the pre-ringing (B3). Providing the () with both a smooth start and a smooth end (C1), and convolving it with its inverse filter (C2) removes both the pre- and the post-ringing (C3).</p

Experimental measurements of the spectral effect of the piriform fossae.

<p>Experimental measurements of MRI-based 3D-printed VT of Barnaby, singing on the vowels as in /fuːd/ (A) and /niːp/ with (greyscale) and without left (red) or right (blue) piriform fossa.</p