Sound absorption by tree bark

Scattering of sound waves by trunks is a main physical factor leading to sound pressure level reduction by tree belts, and it has been shown before that the absorbing properties of the trunks are relevant in this respect. However, detailed information on bark absorption is currently very scarce. Therefore, laboratory experiments were conducted with an impedance tube to measure the bark’s sound absorption of various tree species, including characterizations of bark thickness, roughness, tree age and moss coverage. Preliminary measurements were made to come to a reproducible sample handling procedure. The measurements show that the absorption (at normal incidence) is generally below 0.1 for the species considered and rather frequency independent below 1 kHz. There are statistically significant differences in the averaged absorption between species. Overall, the barks of conifers absorb sound slightly better than in case of broadleaved species. The most relevant visual predictor for the sound absorption of bark is its roughness. Interestingly, moss grown barks provide a strong increase in absorption in the frequency range up to 800 Hz. Especially in dense tree belts, bark absorption might have an influence on the final noise shielding performance

Interactive soundscape augmentation of an urban park in a real and virtual setting

Inappropriate soundscapes are able to strongly deteriorate the user experience in parks. A possible remediation is adding positively perceived sounds. The case of an urban park, fully surrounded by road traffic noise sources, was studied to explore the potential of adding natural sounds in an interactive way. A preliminary test was conducted in the lab with Virtual Reality (VR) glasses and headphones. The audio-visual representation of the real environment was obtained by combining binaural recordings with first-order ambisonics and 360-degree video camera footage. The users were allowed to mix in eight types of natural sounds until their personal optimized soundscape was composed. This was done in a very similar setup as in the (real) park. The loudspeaker augmenting the sound environment in the park was steered with a smartphone application. This app ensured the user ’s presence near the loudspeaker and allowed to gather more detailed assessments of the perceived sound environment through questionnaires. This combination of experiments allowed checking the validity of VR that is becoming increasingly popular in audio-visual interaction studies. In addition, the most preferred natural sounds and the way they influenced environmental noise perception were analyzed

The impact of chronic RV pressure overload on right and left heart morphology and function

peer reviewe

Association of decreased bodyweight-independent tricuspid annular plane systolic excursion (TAPSE) measured in M-mode with clinical signs of heart failure and cardiac death in dogs with pre-capillary pulmonary hypertension.

peer reviewe