HCI-Lect-03.pdf

HCI LECTURE 03 1 Hearing The sense of hearing is often considered secondary to sight, but we tend to underestimate the amount of information that we receive through our ears. Close your eyes for a moment and listen. – What sounds can you hear? – Where are they coming from? – What is making them? 2 H...

HCI LECTURE 03 1 Hearing The sense of hearing is often considered secondary to sight, but we tend to underestimate the amount of information that we receive through our ears. Close your eyes for a moment and listen. – What sounds can you hear? – Where are they coming from? – What is making them? 2 Hearing As I sit at my desk I can hear cars passing on the road outside, machinery working on a site nearby, the drone of a plane overhead and bird song. But I can also tell where the sounds are coming from, and estimate how far away they are. from the sounds I hear I can tell that a car is passing on a particular road near my house, and which direction it is traveling in. The auditory system can convey a lot of information about our environment. But how does it work? 3 The human ear hearing begins with vibrations in the air or sound waves. The ear receives these vibrations and transmits them, through various stages, to the auditory nerves )‫(االعصاب السمعية‬. The ear comprises three sections, commonly known as the outer ear, middle ear and inner ear. 4 The human ear The outer ear is the visible part of the ear. It has two parts: the pinna, which is the structure that is attached to the sides of the head, and the auditory canal, along which sound waves are passed to the middle ear. The outer ear serves two purposes. First, it protects the sensitive middle ear from damage. – The auditory canal contains wax )‫ (شمع‬which prevents dust, dirt and over-inquisitive insects )‫ (الحشرات‬reaching the middle ear. Secondly, the pinna and auditory canal serve to amplify some sounds. 5 The human ear The middle ear is a small cavity )‫ (تجويف‬connected to the outer ear by the tympanic membrane)‫(الغشاء الطبلى‬, or ear drum )‫(طبلة االذن‬, and to the inner ear by the cochlea )‫(القوقعة‬. Within the cavity are the ossicles )‫(عظيمات‬, the smallest bones in the body. Sound waves pass along the auditory canal and vibrate the ear drum which in turn vibrates the ossicles )‫(عظيمات‬, which transmit the vibrations to the cochlea, and so into the inner ear. ‫(الموجات الصوتية تمر على طول القناة السمعية وتهتز طبلة األذن التي‬ ‫ التي تنقل االهتزازات إلى قوقعة‬،)‫بدورها يهتز على عظيمات (عظيمات‬ ).‫ وذلك في األذن الداخلية‬،‫األذن‬ 6 The human ear the inner ear is filled with a denser cochlean liquid (‫)سائل مكثف اى الخاليا الشعيرية‬. By transmitting them via the ossicles the sound waves are concentrated and amplified. ‫( بارسال الموجات عبر عظيمات تتركز موجات الصوت‬ )‫وتضخيمه‬ 7 The human ear The waves are passed into the liquid-filled cochlea in the inner ear. Within the cochlea are delicate hair cells or cilia that bend because of the vibrations in the cochlean liquid and release a chemical transmitter which causes impulses in the auditory nerve. ‫ (داخل القوقعة خاليا الشعر الحساسة أو أهداب أن تنحني بسبب‬ ‫االهتزازات في السائل من ثم ارسال اشارات الكيميائى التى تسبب‬ ).‫النبضات في العصب السمعي‬ 8 Processing sound As we have seen, sound is changes or vibrations in air pressure. It has a number of characteristics which we can differentiate. Pitch (tone ‫ )نغمة‬is the frequency of the sound. A low frequency produces a low pitch, a high frequency, a high pitch. Loudness is proportional to the amplitude )‫(سعة‬ of the sound; the frequency remains constant. Timbre )‫(جرس‬relates to the type of the sound 9 Processing sound The human ear can hear frequencies from about 20 Hz to 15 kHz. The auditory system performs some filtering of the sounds received, allowing us to ignore background noise and concentrate on important information. > 10 Touch The third and last of the senses that we will consider is touch or haptic perception. Although this sense is often viewed as less important than sight or hearing, imagine life without it. Touch provides us with vital information about our environment. It tells us when we touch something hot or cold, and can therefore act as a warning. >> 11 Touch It also provides us with feedback when we attempt to lift an object, for example. Consider the act of picking up a glass of water. If we could only see the glass and not feel when our hand made contact with it or feel its shape, the speed and accuracy of the action would be reduced. 12 Touch The apparatus of touch differs from that of sight and hearing in that it is not localized. We receive stimuli through the skin. The skin contains three types of sensory receptor: – thermoreceptors respond to heat and cold. – nociceptors respond to intense pressure and pain. – mechanoreceptors respond to pressure. 13 Touch There are two kinds of mechanoreceptor, which respond to different types of pressure. Rapidly adapting mechanoreceptors respond to immediate pressure as the skin is indented. These receptors also react more quickly with increased pressure. However, they stop responding if continuous pressure is applied. Slowly adapting mechanoreceptors respond to continuously applied pressure. 14 Thank You 15