The consequences of different size distributions are apparent when aerosol mass concentration is reported (Fig. , see Extended Data Table and). This comparison is most important when considering the potential of the different activities to transmit infection. Speaking and singing generate statistically significant differences in mass concentrations of aerosol at similar volumes; however, these are modest (median singing values only a factor of 1.5-3.4 times larger than speaking) relative to the effects of the volume of vocalization (a factor of 20-30 increase). Converting from a number concentration to a mass concentration for breathing results in the mass concentration range shifting to lower values relative to speaking and singing, a consequence of the different size distributions associated with voicing and breathing (median values 24 and 36 times higher for speaking and singing at the highest volume level, respectively, compared with breathing).