The use of personal hearing protection devices (HPDs) is often recommended to protect workers' hearing from noise-induced damage when no other means of reducing noise levels at the source is effective. The effects of HPDs on speech communication cannot be neglected in spite of their benefit in reducing the risk of hearing loss. While much research has been directed at speech perception, much less is known on how HPDs affect speech production. The tendency of talkers to raise their vocal effort in noise, known as the Lombard effect, is often disrupted by HPDs due to their occlusion effect and the lower noise at the ears as well as the attenuated feedback from one’s own voice. Three main knowledge gaps are addressed in this thesis. The first gap is to characterize speech produced by talkers with or without HPDs under realistic acoustic conditions while immersed in an external noise field. The second gap is to evaluate more comprehensively speech production under protected and unprotected talker and listener ear conditions in different types of fluctuating and continous noises. The third gap is to assess the alterations in the characteristics of speech produced by talkers wearing level-dependent HPDs set at different transmission gain settings and in comparison with passive HPDs. This thesis extends methods used to recover Lombard speech elicited in an external noise field. For this purpose, two noise suppression methods, direct waveform subtraction (DWS) and adaptive noise cancellation (ANC), were found to adequately remove noise from speech recorded for SNRs as low as −10 dB. Moreover, this work contributes new knowledge on the effects of conventional passive HPDs on speech production. When talker wears HPD in noise then speech level were found to decrease by up to 9 dB in continuous noises and by 7 dB in fluctuating noises compared to open ears, while speech levels were found to increase by about 5 dB in all noises when the listener wears HPD. Furthermore, changes in pitch and spectral levels were consistent with changes in speech levels. The effects of level-dependent HPD on speech production, depending on the chosen transmission gain setting, revealed that it led to smaller decrease in talkers’ speech levels in noise compared to conventional passive HPD. These findings indicate that the level-dependent HPDs may impede communication less than conventional passive HPDs, while providing protection against high levels of noise.

El objetivo de este trabajo de investigación es validar el proyecto de negocio de instalación y comercialización de ventanas que reducen el ruido, Easy Windows dirigido a los hogares de Lima Metropolitana pertenecientes a los segmentos A y B que presentan el problema de ruidos externos en su hogares. Para ello, se realizaron diferentes metodologías cualitativas y cuantitativas como entrevistas a profundidad, encuestas y la creación de un producto mínimo viable para confirmar la existencia del problema y confirmar la hipótesis. Así también se comprobaron algunos objetivos específicos como la disposición del mercado objetivo a invertir en una solución a los ruidos externos. Además de comprobar cuales son los principales factores en los que se ven afectados los hogares a causa de este problema. El problema de contaminación sonora existe varias décadas atrás pero se ha agudizado a raíz del confinamiento producto de la pandemia Covid 19, ya que se han generado nuevos hábitos y por ende nuevas necesidades. Es así que existe una gran oportunidad de negocio al solucionar este problema a través de la comercialización de ventanas de aluminio y vidrio que reducen el ruido. Finalmente, nuestro plan de negocios arroja resultados financieros óptimos con una TIR de 141.54%y un VAN de $ 598,609. Por lo tanto, podemos concluir que, de acuerdo al análisis realizado en el presente proyecto, el desarrollo de la empresa Easy Windows es viable económicamente. / The objective of this research work is to validate the business project for the installation and sell of windows that reduce noise, Easy Windows, aimed at homes in Metropolitan Lima belonging to segments A and B that present the problem of external noise in their homes. For this, different qualitative and quantitative methodologies were carried out, such as in-depth interviews, surveys, and the creation of a minimum viable product to confirm the existence of the problem and confirm the hypothesis. Thus, some specific objectives were also verified, such as the willingness of the target market to invest in a solution to external noise. In addition to verifying which are the main factors in which homes are affected because of this problem. The noise pollution problem has existed for several decades but has worsened as a result of the confinement caused by the Covid 19 pandemic since new habits and therefore new needs have been generated. Thus, there is a great business opportunity to solve this problem through the commercialization of aluminum and glass windows that reduce noise. Finally, our business plan produces optimal financial results with an IRR of 141.54% and an NPV of $ 598,609. Therefore, we can conclude that, according to the analysis carried out in this project, the development of the Easy Windows company is economically viable. / Trabajo de investigación