Yes, a funnel can amplify sound in both directions, depending on how it is used. The key factor is how the sound waves interact with the shape and properties of the funnel.
When using a funnel to gather sound, such as in the case of a hearing aid, the funnel acts as a sound collector. The wider end of the funnel captures a larger area of sound waves and funnels them into a smaller area, thereby increasing the sound pressure and directing the sound waves towards the listener's ear. This helps to amplify and focus the sound, making it easier for the listener to hear.
On the other hand, when a funnel is used in reverse, as in a gramophone, it can amplify the sound produced by a needle or stylus. In this case, the sound vibrations produced by the needle are transmitted to the wider end of the funnel. The funnel's shape and acoustic properties, such as its material and dimensions, can help to concentrate and direct the sound waves toward the narrower end. This causes the sound to be amplified and projected more effectively, improving the overall volume and quality of the sound produced by the gramophone.
So, while the specific usage and design of the funnel may vary, it can indeed amplify sound in both ways depending on the context and application.