After recording several words with [f] and [v] from Hindi and English, you are now inspecting the spectrograms.

After recording several words with [f] and [v] from Hindi and English, you are now inspecting the spectrograms. You realize that some of the words which speakers told you ended in a [v] acoustically look (on a spectrogram) and sound (on isolated playback) more like an [f]. Relate this phenomenon to the relative difficulty of voicing a fricative.