Final answer:
Sound A (90 dB at 50 Hz) is objectively more intense and thus likely to be perceived as louder than Sound B (70 dB at 800 Hz), despite the human ear's varying sensitivity to different frequencies. The correct option is A).
Step-by-step explanation:
When comparing the loudness of two sounds, Sound A (90 dB at 50 Hz) and Sound B (70 dB at 800 Hz), it's important to consider both the decibel level and the frequency of the sounds.
The decibel level directly measures the intensity of the sound, with higher decibels indicating a more intense, and thus generally louder, sound. Frequency, on the other hand, affects the perceived loudness to our ears, as human hearing is more sensitive to frequencies in the range of 2000 to 5000 Hz.
Since Sound A is 90 dB and Sound B is 70 dB, we can conclude that Sound A is objectively more intense. However, because Sound A is at a low frequency (50 Hz) where our ears are less sensitive, and Sound B is closer to the range where our ears have more sensitivity,
the perceived loudness could differ from the intensity difference. Still, a 20 dB difference is quite significant, and Sound A would likely be perceived as the louder sound due to the much higher intensity level.
Therefore, the answer to "Which is louder: sound A (90 dB at 50 Hz) or sound B (70 dB at 800 Hz)?" would be A) Sound A (90 dB at 50 Hz), as it has a significantly higher decibel level which typically correlates with loudness, despite the frequency considerations.
Additionally, the concept that a change in sound level of 3 dB is easily noticed supports Sound A being perceived as louder too. The perception of loudness is indeed subjective to an extent, but in this case, the large difference in intensity levels is the deciding factor. Option A) is the correct one.