How should I understand these acoustic and perceptive terms from phonetics?

Question

So, while reading the New Grammar of Spanish Language (a book from a very influential institute of the Spanish languague: Royal Spanish Academy) I found out these terms (they'll be in bold) from acoustic and perceptive phonetics. So, paraphrasing (because the original text is in Spanish):

In acoustic phonetics, sounds are classified based on: the amplitude (the energy of the vibration of the air's molecules that cause the sound, made by exhalation), the frecuency (determined by the opening and closure of the vocal chord) and the time. This amplitude is filtered by pharyngeal, oral and nasal cavities, creating the formants: the frequency bands of the sound.

So, based on the amplitude, frequency and time, we can classify sounds by their origins (perodical/aperiodical [sonorous/dull])[...]

In perceptive phonetics: we can classify sounds based on the intensity, tone, timbre [...]

(RSA, 2009)

My question is, how should I understand those terms in simple words? (analogies are welcome). They're too technical. I'm searching for non-technical, easy definitions.

I'm not even sure what "amplitude" and "frequency bands" really mean (although, I know they're terms connected to physics) and in the case of the term "frequency", I think they're using the same term people use on physics but I'm neither sure and, on the other hand, I don't know if when they say "aperiodical" and "periodical", they're classifying them based on the time of the sounds.

In the case of the perceptive terms, instensity sounds like "strength" and I know tone and timbre are qualities and with the tone we can classify sounds in high and low-pitched sounds and with the timbre we can distinguish between two sounds of the same frequency and intensity (such as the sound of a trumpet and a violin) but, what are exactly these qualities?

Sorry if something sounds confusing; if my English is not the best (my first language is Spanish and I'm translating the paragraphs); if I didn't ask correctly; or, if I posted this question in the wrong section (I'm not sure if it belongs here or in StackExchange's physics or Spanish sections).

Answer 1

The basic acoustic fact is that any sound can be analyzed as a sum of sine wave components at a given frequency and amplitude. A very simple example is a single-component sine wave at 100 Hz and 70 dB (taking a few shortcuts here). Here is a reminder graph. If the sound is quieter, it might only go up to 1/2 (on that graph), or up to 2 if it is louder. The amplitude is about the range of that sine wave. The frequency is about how many times the component repeats per second: 1 Hz = 1 time per second, 100 Hz is 100 times per second. Most sounds (other than what you hear when you're taking a hearing test) have many components, not just 100 Hz, but also 200 Hz, in fact at all possible frequencies up to a limit having to do with the "quality" of the recording (4410 Hz vs 22050).

Because there are infinitely many (theoretical) components to any real sound, to talk sensible about them we talk about "frequency bands". In vowels there will be about 5 areas where there is most of the energy (where the amplitude of the component is highest) and these concentrations are very clear, as you see in these pictures (really, only 3 of those bands, known as formants, are obvious here). In this picture, you see consonants [s,x,v,ð] between vowels: you can see that these consonants also have distinct patterns of darkness (higher amplitude at a given frequency, up to 8000 Hz).

So basically, it's about different pitches, and more energy at higher vs lower pitches. The other terms are complications. Periodic sounds are ones where the vocal folds continuously vibrate: vowels, liquids, nasals, maybe voiced stops. If there isn't (mostly) regular vocal fold vibration, then the sound is "aperiodic" (e.g. /s,t/ and usually /z/). "Intensity" is related to amplitude, just as pitch is related to frequency: basically it's differences of scaling. We especially talk about amplitude in perceptual terms, because things that are physically twice as energetic are just a little bit louder. So intensity is amplitude from a perceptual perspective.

When you get to "tone" and "timbre", you're far enough from technical linguistics that we don't know what the author means. Some languages (like Chinese) use vowel-frequency differences linguistically, and everybody can make their voice "go up" or "go down". That would be "tone", in the linguistic sense. "Timbre" is, uhhh... probably something about voice quality, but that is not a feature of Spanish, for instance (it is a feature of Hmong). It is a thing that distinguishes how individual's sound (James Cagney vs. Clint Eastwood), and does have some linguistic relevance in some of the little-studied languages.