Evaluation of sound attenuation effect in recording studios: case of angel FM station in Kumasi, Ghana

Cities in developing countries like Ghana experience severe environmental noise pollution resulting predominantly from a blend of exponential increase in road traffic volume, industrial, commercial and residential activities that are associated with thick population trends. High levels of noise pollution can have detrimental effects on human beings. Buildings that house noise sensitive activities such as recording studios in city centres need to be designed to provide protection from high ambient noise levels that may interfere with speech communication. Cities and towns in Ghana have about one hundred and eighty Frequency Modulation (FM) stations that are invariably sited in the Central Business Districts (CBD) that happen to be in very noisy environments. The study investigated prevailing sound levels in the recording studio and associated spaces in an FM Station in Kumasi, the second largest city in Ghana. Data collection approaches involved monitoring of indoor and outdoor sound levels, interviewing of residents and workers of the community to assess their perception of noise levels. In addition measured drawings of the facilities and some observations were undertaken. The data was analysed within the context of the study objectives. Monitored sound levels were compared to set standards by World Health Organization (WHO). The WHO permissible ambient noise level limits of 45dB to 55dB and 55dB to 65dB for residential and commercial zones respectively were exceeded for all outdoor monitored values. However, the sound attenuating capabilities of the FM Station building maintains sound levels in the recording studios that are within permissible sound limits. It is expected that the findings of this study will contribute in assisting designers to make more objective design decisions at the preliminary phase of a studio building project, especially in very noisy urban environments

The CZTS Thin Films Grown by Sulfurization of Electrodeposited Metallic Precursors: The Effect of Increasing Tin Content of the Metallic Precursors on the Structure, Morphology and Optical Properties of the Thin Films

A study has been carried out to investigate the influence of the amount of Sn in the precursor solution, on some physical properties of CZTS films grown by sulfurization of electrodeposited metallic precursors. The growth of the CZTS samples was achieved by sequential electrodepositon of constituent metallic layers on ITO glass substrates using a 3-electrode electrochemical cell with graphite as a counter electrode and Ag/AgCl as the reference electrode. The Sn-content in the metallic precursor was varied by varying the deposition time of Sn. The stacked elemental layer was then soft annealed in Argon at 350 °C, and subsequently sulfurized at 550° C to grow the CZTS thin films. The structure, morphology and optical properties were investigated. X-ray diffraction studies revealed that, irrespective of the Sn content all the films were polycrystalline and exhibited the Kesterite CZTS structure with preferred orientation along the (112) plane. However, there was an increase in the amount of peaks indexed to the undesirable secondary phases, as the Sn content in metallic precursor was increased. Optical absorption measurements revealed the existence of a direct transition with band gap values decreasing from 1.74 eV to 1.25 eV with increasing amounts of Sn. The lower value for the band gap was attributed to the presence of secondary phases formed in addition to the CZTS film. Morphology of the sulfurized films showed a compact and rocky texture with good coverage across the entire substrate. However, CZTS films with a higher Sn content appeared to have a molten metallic surface with deep cracks which could have adverse effects on the electrical properties of the film. EDAX analysis showed all the films were consistent with the formation of CZTS. It is evident from all the characterization techniques that increasing the Sn content of the stacked metallic precursors beyond stoichiometric amounts had an adverse effect on the structural and optical properties of CZTS films grown by this technique