Final answer:
Researchers control environmental factors like sounds, smells, and temperature to reduce situation noise in experiments, ensuring the validity of the results by minimizing confounding variables.
Step-by-step explanation:
A researcher's attempt to control sounds, smells, and even temperature in a testing environment is aimed at reducing situation noise. Situation noise refers to extraneous variables that can interfere with the experimental conditions and potentially obscure the effects of the independent variable. An experiment needs to be controlled to ensure that the only difference between the experimental and control groups is the experimental manipulation. Controls, such as the use of a placebo, are essential to eliminate confounding variables and allow researchers to attribute any differences in outcomes to the experimental treatment rather than to other factors. This meticulous control of the environment is crucial for achieving valid and reliable results, thereby increasing the test's internal validity.