if 2 waves result in a wave with smaller amplitude is it destructive superposition?

In many places I see written that for destructive superposition to occur, waves must be 180 degrees out of phase. Is that the only way destructive superposition occurs? Shouldn't the waves cancel out in such a situation? Under what condition would a wave he created which has less amplitude than each component wave?
And would the process of such creation be called destructive superposition?

can anyone answer these two questions?

Explain why you do not see any interference between the light from two light bulbs connected to the same power supply.

Explain why you can hear interference between sound from two loudspeakers that are connected to the same source

HELP!!

May I ask where you found these questions?
I'm not 100% sure, but I think that the answer to the first question is because light is emitted in bursts of energy. Therefore the light from the two different light sources aren't coherent, so no visible interference is seen. Interference happens, but it's just all jumbled up.

I'm not too confident with the second question, sorry. I hope this helps a little

Coherence is certainly one factor. However, I think probably what they're looking for in this case is that interference is most visible if the distance between the two sources is close to the wavelength of the emitted signal. The wavelength of light is on the order of hundreds of nanometres whereas the wavelength of sound is on the order of several metres, so in a normal-sized room the effect is going to be more noticeable for sound than for light.

Okay thanks. any idea for question 2?

The sounds from the two speakers are coherent because they come from the same original source.
The light from the two light bulbs is not coherent because the light is emitted in random pulses with random phase differences from both. To make light coherent you need to take the light from a single source (one point on one bulb) and split it into two, as in the double slit experiment.

The phenomenon is called interference
To observe constructive or destructive interference the sources need to be coherent and, ideally, of the same amplitude.
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Superposition is the name given to the way in which the resulting amplitude of a wave at a point, formed by the combining of two separate waves, is found by adding adding the amplitudes of the two waves at that point. This needs to take into account the fact that the amplitude can be positive or negative at that point.
So if the two combining waves have amplitude A, by superposition the resulting wave can have a maximum amplitude of 2A (=A+A) and a minimum of zero. (=A - A)

Zero amplitude is, strictly speaking, destructive interference. This arises from the original experiments where you obtained light and dark fringes with light. The dark fringes were called areas of destructive interference because no light was seen there. In fact, the intensity of the light in the fringe region is not on - off - on - off, like a zebra crossing, and the dark fringes are not uniformly dark. They appear that way because the naked eye is not sensitive enough to distinguish the subtle variation in the intensity of the light in the fringes.
So yes, interference can produce, by superposition, any intensity of light (or sound) from zero to a value equal to the sum of the amplitudes of the the two waves.